A study of Australian male World War II veterans was conducted to assess clinically the gastrointestinal ill-effects which were present 40 years after the stress of internment as prisoners of war of the Japanese. A random sample of 170 surviving members of the captured Eighth Army Division resident in Sydney in 1983 (ex-POW) was compared with a similar sample of veterans who fought in Southeast Asia during the War, but were not imprisoned (non-POW). Duodenal ulcers and strongyloidiasis were more prevalent in the ex-POW group than in the non-POW group. The increased rate of duodenal ulcer (24.7%, compared with 10.5%; P = 0.0005) was confirmed by a higher proportion of ex-POWs currently taking cimetidine (9.0%, compared with 2.3%; P = 0.008). Strongyloidiasis had been found in 9.7% of all veterans, but in 15% of ex-POWs and in 19% of those who had worked on the Burma-Thailand railway. No other significant differences in gastrointestinal disease were found.