Outpatient illness rates aboard carriers and destroyers/frigates during the Vietnam conflict were contrasted with rates for similar ships in the same geographical region subsequent to the ceasefire. Both large and small ships exhibited higher overall outpatient rates after the conflict, although this difference did not reach a level of significance among carriers. Among the smaller ships the individual categories of infective and parasitic disorders, respiratory diseases, and skin and subcutaneous tissue problems yielded significantly higher rates after the conflict. The rate for accidents was significantly higher aboard carriers during combat operations than the period following the cease-fire. Across both sizes of ships, accidents accounted for a larger percentage of outpatient visits during the conflict, while skin disorders were responsible for a larger proportion of the post-conflict visits.