Objectives: To examine among immigrants and others seeking primary care: (1) the prevalence, types, and predictors of traumatic life events; and (2) the relations among traumatic life events, psychiatric disorders, and utilization of primary care services. Design: Survey with structured diagnostic interview. Setting: Community-based, university-affiliated primary care clinic in southern California. Participants: Fourteen hundred fifty-six adult patients representing 4 ethnic groups (Mexican immigrants, Central American immigrants, US-born Latinos of Mexican descent, and US-born non-Latino whites). Dependent Measures: Rates of traumatic events measured with the Posttraumatic Stress Disorder section of the Diagnostic Interview Schedule; psychiatric disorders identified by the Composite International Diagnostic Interview using Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition criteria; physical functioning (Short Form Health Survey); and the number of medical clinic visits during a 6-month period. Results: Nearly 10% of patients had experienced a traumatic event in the previous year, and 57% had experienced at least 1 during their lifetimes. The most common forms of trauma were interpersonal violence occurring outside the family (21%), acute losses or accidents (17%), witnessing death or violence (13%), and domestic violence (12%). When compared with the US-born non-Latino whites, Mexican immigrants were half as likely, and Central American immigrants were 76% more likely, to report having experienced a traumatic event. Married individuals were significantly less likely to report traumas. Traumatic experiences, female gender, and non-Latino ethnicity were associated with the presence of a psychiatric disorder. One-year and lifetime psychiatric disorders were associated with poorer physical functioning and an increased number of clinic visits during a 6-month period. Conclusioons: Traumatic life events are common and associated with psychiatric disorders other than posttraumatic stress disorder in an ethnically diverse sample of primary care patients. Psychiatric disorders, in turn, are strongly associated with poor physical functioning and higher rates of primary care utilization. Screening for traumatic experiences should accompany assessments of psychiatric disorders to ensure adequate treatment of patients seeking primary care services.