As the first in a series of studies examining the military course and outcome of hospitalization for a mental disorder, we provide a comprehensive overview of psychoses among active duty Navy enlisted personnel with a first hospitalization between 1980 and 1988. Patients' military service and medical histories were tracked through 1992 to provide at least 4 years of follow-up data. Incidence rates varied greatly over time and across gender, age, race, and diagnostic groups. A large increase in the rate of affective psychosis for women was in sharp contrast to marked declines in rates for drug psychoses, schizophrenia, and other nonorganic psychoses and to the relatively stable rates for alcohol psychoses and paranoid states. Psychoses had a very significant negative impact on naval careers.