The prevalence rates varied by age, sex, race and ethnicity, and region of residence. People over age 25, males, and blacks and Hispanics had higher rates than those who were younger, female, or of other racial groups. During the 15-month observation period, the seroprevalence did not change significantly, either for the whole group or when subgroups were analyzed. Volunteers for military service underrepresent the groups with the highest prevalence of HIV infection and do not equally represent all socioeconomic and demographic groups. Monitoring trends in infection rates remains important. Table, figures, and 5 references.