Disease and non-battle injury rates were computed for ships of the British Royal Navy which were deployed during wartime and peacetime operations. The wartime sick list admission rates were lower aboard carriers, battleships, and cruisers when compared with their counterparts deployed in peacetime; rate differences for battleships and cruisers were statistically significant (p < 0.05). Several categories of disease also yielded significant differences in the wartime/peacetime contrasts. Infections and parasitic disorders aboard carriers, skin diseases aboard battleships, and skin diseases, injuries, and generative system disorders occurring on cruisers were all lower during wartime than on peacetime deployments. Illness rates also varied by ship type, with the lowest rates evidenced aboard carriers.