Twenty seven obsessive-compulsive disorder (OCD) patients were studied at the Instituto Mexicano de Psiquiatría in Mexico City. This is the first sample of OCD patients studied in Latin America. There was a significant sex ratio difference and a significant difference in the type of obsessions and compulsions displayed by males and females. Co-morbidity data demonstrated a high frequency of obsessive-compulsive personality disorders, depression, sexual abuse, suicidal attempts and neurological damage. Approximately one third of OCD cases demonstrated a positive family history. There was a higher than expected frequency of first degree relatives affected with OCD. In addition, this study may support the hypothesis that OCD and tics are genetically related.