An epidemiologic analysis of accidental injury hospitalizations was conducted to determine if risk varied by seniority, cause, or duty status for major operational and support activities in the US Navy. Computerized archival medical data were used to select all male enlisted personnel who were hospitalized due to an accidental injury during the period 1977 to 1979 (N = 21,295). Comparison of hospitalization rates between shore-based and sea-based personnel revealed that duty aboard destroyers, replenishment ships, and conventional carriers significantly increased an individual's risk of injury. An inverse relationship was observed between injury risk and seniority. Athletic, automobile, and motorcycle accidents accounted for 63% of all off-duty hospitalizations; machinery, falls, and miscellaneous accidents were the most frequent (56%) causes of on-duty hospitalizations. A positive and significant correlation observed between on-duty and off-duty hospitalizations suggests that common personal attributes may operate in both settings to exacerbate injury risk. Identification of high-risk groups will help focus preventive and corrective efforts.