OBJECTIVE: Major depression is a frequent and disabling psychiatric disorder in the United States. This report examines the prevalence and risk factor profile of both pure and comorbid major depression according to data from the National Comorbidity Survey. METHOD: To estimate the prevalence of psychiatric comorbidity in the United States, a national sample of 8,098 persons 15-54 years of age from the 48 conterminous states was surveyed with a modified version of the Composite International Diagnostic Interview. Results: From the survey data the prevalence of current (30-day) major depression was estimated to be 4.9%, with a relatively higher prevalence in females, young adults, and persons with less than a college education. The prevalence estimate for lifetime major depression was 17.1%, with a similar demographic distribution. Both 30-day and lifetime prevalence estimates were higher than estimates from the earlier Epidemiologic Catchment Area study. When pure major depression was compared with major depression co-occurring with other psychiatric disorders, the risk factor profiles exhibited clear differences. CONCLUSIONS: These findings suggest a greater burden of major depression in community-dwelling persons than has been estimated from previous community samples. The risk factor profile showed significant differences between persons with pure and combined major depression.