Background: Previous research has questioned the validity of diagnostic measures for autism spectrum disorder (ASD) among adults. This study examined the correspondence between several measures and clinician diagnosis. Methods: We conducted a retrospective chart review for 93 adults (18-61 years; 72% male) who received an ASD evaluation at a specialty outpatient clinic. Thirty-one individuals (33%) in the sample were diagnosed with ASD. We compared participant scores on the Autism Spectrum Quotient (AQ), the Ritvo Autism Asperger's Diagnostic Scale-Revised (RAADS-R), and the Autism Diagnostic Observation Schedule (ADOS) to clinician diagnosis of ASD. We calculated sensitivity, specificity, and area under the curve (AUC) for each measure. Results: Participants diagnosed with ASD scored significantly higher, on average, on the ADOS than those who were not diagnosed with ASD, but not on the RAADS-R or AQ. The AUC was relatively low for each measure: ADOS = 0.69 (95% confidence interval [CI] 0.58-0.81), RAADS-R = 0.58 (95% CI 0.46-0.72), and AQ = 0.40 (95% CI 0.28-0.52). Sensitivity and specificity of all three measures were in the poor to fair range. When dichotomized at the optimal cutoffs for this sample, the ADOS had a sensitivity of 0.65 and a specificity of 0.76; the RAADS-R had a sensitivity of 0.52 and a specificity of 0.73; and the AQ had a sensitivity of 0.45 and a specificity of 0.52. Conclusions: Results of the study suggest that clinicians should not rely solely on self-report measures or the ADOS when diagnosing adults on the spectrum. Further development of measures is needed, including selfreport measures with higher diagnostic validity, that are sensitive across age, gender, and cognitive functioning, and that differentiate autism from psychiatric diagnoses. Lay SummaryWhy was this study done?Diagnosing adults with autism spectrum disorder (ASD) is difficult. Other research has suggested that the few measures that exist for autistic adults may not be very effective for accurate diagnoses. We wanted to see how closely the results of commonly used ASD assessment tools compared with clinical diagnoses in a real-life outpatient setting. What did the researchers do?This study looked at adults who went to an adult ASD outpatient clinic for an initial ASD diagnosis over 3 years. Of these 93 adults, one-third were diagnosed as autistic. As part of the evaluation, all participants completed two commonly used autism screening surveys-the Autism Spectrum Quotient (AQ) and the Ritvo Autism Asperger's Diagnostic Scale-Revised (RAADS-R)-and took part in a semistructured diagnostic interview called the Autism Diagnostic Observation Schedule (ADOS). The clinicians also collected additional information and, when possible, spoke to family members before jointly making a diagnosis. The researchers compared how those diagnosed with ASD and those who were not diagnosed with ASD scored on the AQ, the RAADS-R, and the ADOS. What were the results of this study?Although adults on the spectrum scored higher on average on the ...