The objective of this study was to assess the extent of referral bias by comparing children and adolescents with Obsessive Compulsive Disorder (OCD) ascertained through a specialized pediatric OCD and a general child psychiatry clinic. Subjects were juveniles meeting DSM-III-R and DSM IV criteria for OCD referred to a general pediatric psychopharmacology clinic and to a specialized OCD clinic within the same academic medical center. Subjects were evaluated clinically and with structured diagnostic interviews using the Kiddie SADS-E. OCD was identified in 8.6% of the general psychiatry clinic subjects. The only differences between ascertainment sources in clinical or sociodemographic characteristics of OCD subjects were higher rates of social phobia and ADHD in the non-specialized clinic, while specialty clinic subjects had a greater lifetime severity of OCD and were more likely to have received treatment of their OCD. Because we found limited evidence for referral biases, our results suggest that findings from studies using either of these sources may generalize to the other. It also suggests that pooling subjects from the two sources is justified. Nevertheless, because some group differences did emerge, researchers should acknowledge referral bias as a potential limitation of their work.