This research aimed to comprehensively explore psychopathology in Williams syndrome (WS) across the life span and evaluate the relationship between psychopathology and age category (child or adult), gender, and cognitive ability. The parents of 50 participants with WS, ages 6-50 years, were interviewed using the Schedule for Affective Disorders and Schizophrenia for School-Age Children. The prevalence of a wide range of Axis I "Diagnostic and Statistical Manual of Mental Disorders" (DSM-IV; American Psychiatric Association, 1994) disorders was assessed. In addition to high rates of anxiety and attention-deficit/hyperactivity disorder (38% and 20%, respectively), 14% of our sample met criteria for a Depressive Disorder and 42% of participants were not experiencing any significant psychopathological difficulties. There was some evidence for different patterns of psychopathology between children and adults with WS and between males and females. These relationships were largely in keeping with those found in the typically developing population, thus supporting the validity of applying theory and treatment approaches for psychopathology in the typically developing population to WS. (Contains 3 tables.)