An epidemiologic survey of the lifetime and six-month prevalence rates of several psychiatric disorders was conducted in Puerto Rico. This study, carried out in 1984, applied selected schedules of a Spanish translation of the Diagnostic Interview Schedule to a stratified, island-wide probability sample of the population. With few exceptions, prevalence rates in this study were similar to those obtained in the US communities studied in the Epidemiologic Catchment Area program. The demographic correlates of the disorders are reviewed, and differences between the results of this study and those of previous studies suggesting a higher rate of mental disorder among Puerto Rican populations are discussed.