Interventional programs providing education and support should be implemented for street children. The study findings indicated that one fifth of the street children had been sexually abused, more than half of them were depressed at the time of the evaluation, and almost the same number had a history of depression in the past. The study found a higher rate of depression in girls than boys. Depressed children had been sexually abused more frequently than non-depressed children, but this study did not find sexual abuse more prevalent in girls. There was a significant relationship between depression in street children and a history of imprisonment or unemployment of the father. Since large numbers of the street children experiencing high psychiatric co-morbidity, as well as depression and sexual abuse, puts a great burden on the society as a whole, giving special attention to this population is crucial for the controlling sexually transmitted diseases and HIV/AIDS. Both governmental and non-governmental organizations should be expected to design and implement comprehensive preventive, therapeutic, and rehabilitative treatment for the morbidities, including education and support for the children and their families. Counseling and support services for families of the unemployed and convicts may also be effective for reducing depression rates and preventing children from entering into the “street” environment. The researchers used the Kiddie-Schedule for Affective Disorders and Schizophrenia (K-SADS) questionnaire and a clinical interview to evaluate depression and sexual abuse in 87 street children in Tehran. The study was limited by the nonrandom sample from only one district of Tehran. Tables, references