Patterns of healthcare use in a sample of young adults entering the US Navy (N = 1137) were examined in a longitudinal survey study. Baseline data provided information about healthcare use as a civilian, whereas follow-up data were used to examine changes in patterns of use over time following entry into the Military Health System (MHS). Entrance into the MHS was marked by increased use of preventive care. Although few systematic differences were noted with respect to socioeconomic status or race/ethnicity, women consistently used more healthcare than did men, and women's use increased more over time; however, this increase was largely driven by pregnancy during military service. Findings suggest that individuals with access to universal healthcare are likely to increase their overall use of services. However, these effects were quite small in absolute terms, and they were strongest for preventive care rather than more intensive and expensive services. Published 2013. This article is a US Government work and is in the public domain in the USA.