Compared mental health characteristics of island Puerto Ricans to three groups from the Los Angeles Epidemiologic Catchment Area Study: Mexican American immigrants, U.S.-born Mexican Americans, and Non-Hispanic whites. The Diagnostic Interview Schedule was used to obtain both diagnostic and symptom scale information about affective disorders, alcohol abuse/dependence, somatization, phobic disorder, and psychotic disorder. Mexican American immigrants had the fewest mental health problems of all groups. Puerto Ricans had more somatization disorder, but less affective and alcohol disorders than U.S.-born Mexican Americans or non-Hispanic whites. Results are considered in the light of selection factors, relative disadvantage of groups and methodological problems.