Persons with developmental disabilities are more frequently abused physically, emotionally and sexually than nondisabled persons (Ammerman, Van-Hasselt, Herson, McGonigle, & Lubetsky, 1989; Sobsey, Gray, Pyper, & Reimer-Heck, 1991). Persons with developmental disabilities are susceptible to the full range of psychiatric disorders (Szymanski, Madow, Mallory, Menolascino, & Pace, 1991). There has been no comprehensive study of posttraumatic stress disorder (PTSD) in this population (Hudson & Pilek, 1990), a recent textbook of mental health and mental retardation does not contain index listings on this condition (Fletcher & Menolascino, 1989), and psychometric tests currently proposed for use with the retarded do not examine for this condition (Aman, Watson, Singh, Turbott, & Wilsher, 1986). In this preliminary study, descriptive data from 51 persons with developmental disabilities who met DSM-IIIR criteria for posttraumatic stress disorder are reported. The majority of cases were detected upon routine initial psychiatric interview and record review. Demographics, family histories, and comorbid psychiatric conditions are described. In this sample all patients who received comprehensive recommended treatment improved.