In order to identify factors associated with the early detection and referral of children with pervasive developmental disorders, a sample of 82 consecutive referrals to an outpatient diagnostic service was studied. All children were thoroughly assessed with the Autism Diagnostic Interview (ADI), standardized psychological tests and direct observations. Data from the ADI on the first symptoms to arouse parental concern and on the first professional advice sought were analyzed. The mean age of children was 19.1 months (SD = 9.4) when the parents first became concerned, and the first professional advice was sought when children were 24.1 months old (SD = 11.7). The most common parental concerns were for speech and language development, followed by abnormal socio-emotional response, and medical problem or delay in milestone. In both bivariate and multiple regression analyses, the mean age of children at first parental concern and professional advice was significantly lower in the presence of mental retardation in the child, of an older sibling in the family, and of first parental concerns for medical problem/delay in milestone. More specific autistic behaviours, child's gender, social class and place of residence did not influence the age of recognition of the disorder in this sample. Health visitors and general practitioners were the first professionals contacted by parents. The implications of these findings for early detection and diagnosis of autism are discussed.