Woman and boy sitting on floor playing with educational toys and paper in a light room.

Continuing Education

CARS-2:

The Childhood Autism Rating Scale, Second Edition

Two women playing and learning with young boys using toys and blocks indoors.

If your child is being evaluated for autism, you may come across the CARS-2 – a widely used and extensively validated autism assessment tool. Understanding what it is, how it works, and what to expect can help you feel informed and prepared as you navigate the diagnostic process.

Smiling woman and child playing and stacking colorful wooden blocks on the floor.

Child and adult assembling colorful wooden blocks into tall towers at a table.

What Is the CARS-2?

The Childhood Autism Rating Scale, Second Edition (CARS-2) is a standardized, clinician-administered rating scale designed to identify autism spectrum disorder (ASD) and estimate its severity. Originally developed by Dr. Eric Schopler and colleagues, the CARS has been a widely used and empirically validated autism assessments since its original publication – and the second edition expands its clinical value to include individuals across a broader range of ages and functioning levels.

‍

The CARS-2 is designed for individuals aged 2 years and older and can be used across virtually all ages and functional levels. Administration typically takes just 5–10 minutes, making it one of the most efficient and accessible autism assessment tools available.

‍

A key strength of the CARS-2 is its ability to distinguish mild-to-moderate autism from severe autism – providing clinicians with a nuanced picture of how autism manifests in a specific individual, not just whether it is present.

The Three Forms of the CARS-2

The CARS-2 includes three distinct forms, allowing clinicians to select the most appropriate version based on the individual's age, verbal ability, and cognitive functioning:

CARS2-ST, Standard Version:

The Standard Version is equivalent to the original CARS and is used for individuals younger than 6 years of age, as well as older individuals with communication difficulties or below-average estimated IQ scores. It is the most commonly used form for young children with autism and for those with more significant autism support needs.

CARS2-HF, High-Functioning Version:

The High-Functioning Version is designed for verbally fluent individuals aged 6 years and older with IQ scores above 80. It was developed specifically to better capture the more subtle social, behavioral, and communication differences seen in individuals on the higher-functioning end of the autism spectrum – who may not be as clearly identified by standard autism rating tools.

CARS2-QPC, Questionnaire for Parents or Caregivers:

The Parent/Caregiver Questionnaire is an unscored companion form that gathers important observational information from parents and caregivers. This information is used to inform the clinician's ratings on the CARS2-ST or CARS2-HF, ensuring that the evaluation captures behaviors observed across settings and over time, not just in the clinical environment where the assessment took place.

What Does the CARS-2 Assess?

Both the CARS2-ST and CARS2-HF consist of 15 items, each evaluating a specific behavioral or developmental domain. Clinicians rate each item on a 4-point scale – from 1 (within normal limits for age) to 4 (severely abnormal for age) – with half-point ratings available for behaviors that fall between categories.

Relating to people

how the individual interacts with others, responds to social cues, and engages in relationships

Imitation

the ability to copy sounds, words, and actions

Emotional response

the “appropriateness” of emotional reactions to situations

Body use

unusual postures, movements, or motor behaviors

Object use

how the individual handles and plays with objects

Adaptation to change

response to changes in routine or environment

Visual response

how the individual uses vision to explore and engage with the environment

Listening response

how the individual responds to sounds and spoken language

Taste, smell, and touch response

sensory sensitivities or unusual responses

Fear and nervousness

level and appropriateness of fear responses

Verbal communication

the use and quality of spoken language

Nonverbal communication

use of gestures, facial expressions, and body language

Activity level

hyperactivity, passivity, or unusual energy levels

Level and consistency of intellectual response

consistency of cognitive functioning

General impressions

the overall degree to which the individual exhibits behaviors associated with autism

What Do CARS-2 Results Mean?

Total scores on the CARS2-ST and CARS2-HF range from 15 to 60. Higher scores indicate more significant autism-related behaviors. Scores for the CARS2-ST are interpreted as follows:

Score below 30 (under age 13) or below 28 (age 13 and older): Indicates minimal to no autism-related behaviors
Score of 30–36.5 (under age 13) or 28–34.5 (age 13 and older): Indicates mild to moderate autism
Score of 37 or above: Indicates severe autism

The CARS2-HF uses version-specific thresholds provided in the CARS2 manual.

‍

It is important to note that CARS-2 scores are one part of a comprehensive diagnostic evaluation. A formal autism diagnosis is made by a licensed clinician based on the totality of the assessment – including direct observation, developmental history, parent input, and other validated tools combined.

Toddler playing with a wooden drum and abacus on a white table indoors.

How Is the CARS-2 Used in the Diagnostic Process?

The CARS-2 is typically used as one component of a comprehensive autism evaluation alongside other validated assessment tools such as the ADOS-2, ADI-R, and GARS-3. It is particularly valuable because it:

Can be administered quickly – typically 5–10 minutes – making it practical for busy clinical settings
Covers a wide age range, from toddlers through adulthood
Distinguishes between mild-to-moderate and severe autism, providing important information for treatment planning
Incorporates direct observation, caregiver input, and developmental history, giving clinicians a multi-dimensional picture
Is widely validated across multiple cultures and populations

Who Administers the CARS-2?

The CARS-2 is administered by qualified clinicians, including licensed psychologists, neuropsychologists, and other credentialed professionals with training in autism assessment.

At Behavior Frontiers, CARS-2 evaluations may be conducted by licensed professionals through our trusted network of diagnostic partners, as part of a variety of comprehensive autism evaluations for families who are ready to begin ABA therapy with Behavior Frontiers following a diagnosis.

CARS-2 and the Path to ABA Therapy

The CARS-2 doesn't just help identify autism – it also helps shape what comes next. By quantifying the severity of autism-related behaviors across 15 key domains, the CARS-2 gives clinicians and families a clearer picture of where support is most needed – and how to prioritize goals in an ABA therapy program.

At Behavior Frontiers, every child's ABA therapy plan is built on a thorough, individualized understanding of who they are and what their goals are. For families who are ready to begin their ABA journey with Behavior Frontiers, we can connect you with our trusted network of licensed diagnostic partners – with autism evaluations available in as little as 4 weeks, and a seamless transition into ABA therapy once your child receives their diagnosis.

What Families Ask Us Most

FAQs

What is the difference between the CARS2-ST and CARS2-HF?

The CARS2-ST (Standard Version) is used for children under 6, as well as older individuals with communication difficulties or below-average IQ. The CARS2-HF (High-Functioning Version) is designed for verbally fluent individuals aged 6 and older with IQ scores above 80 – capturing the more subtle behavioral differences seen in higher-functioning individuals.

Is the CARS-2 a diagnosis?

No. The CARS-2 is a rating scale used as part of a comprehensive autism evaluation. A formal autism diagnosis is made by a licensed clinician based on the full evaluation – including direct observation, developmental history, parent input, and other validated assessment tools.

What age is the CARS-2 appropriate for?

The CARS-2 is designed for individuals aged 2 years and older and can be used across virtually all ages and functional levels.

How does the CARS-2 differ from other autism assessments like the ADOS-2?

The ADOS-2 involves direct, structured interaction between a clinician and the child to observe specific behaviors in real time. The CARS-2 is a rating scale completed by the clinician based on observation and caregiver input – making it faster and broader in scope. Most comprehensive evaluations use multiple tools together to build the most complete and accurate picture.

How can Behavior Frontiers help with the CARS-2?

Behavior Frontiers partners with a network of diagnostic professionals to support autism diagnostic services for families committed to starting ABA therapy with Behavior Frontiers following a diagnosis. Our diagnostic partners conduct comprehensive autism evaluations which may include the CARS-2 and other validated tools. Evaluations are available in as little as 4 weeks, with a seamless transition into ABA therapy once your child receives their diagnosis.