The indirect hemagglutination test was used to study antibody titers to Entamoeba histolytica in different Malaysian populations. 87% of Orang Asli (western Malaysian aborigines) adults and 79% of Orang Asli children with acute amebic dysentery were seropositive. However, significantly fewer children (39%) with amebic dysentery had high titer responses (titer ≥ 1:1,280) than did adults with amebic dysentery (76%). No correlation between proctoscopic severity and amebic titer was found. 44% of asymptomatic family members were seroresponders. Satak, an Orang Asli village located near towns, had significantly more seroresponders (32%) than did the isolated, deep jungle village, Belatim (4%).