The epidemiology of shigellosis in the Jewish and Bedouin populations that coexist in the same geographic region in southern Israel and share the same medical facilities but live separately under different socioeconomic conditions was examined in a retrospective, culture-based study. The average annual attack rate for the four-year period 1989-1992 was 368/100,000 inhabitants. The average annual attack rate among the Jews, who enjoy Western socioeconomic conditions, was 413/100,000 and the disease showed summer and winter peaks. Shigella sonnei caused 3,336 of 4,560 (73.2%) attacks in this group, and the attack rate of Shigella flexneri decreased during the study period. Among the Bedouins, many of whom live in poverty and overcrowding, a single annual summer peak was observed, the average annual attack rate being 197/100,000 and Shigella flexneri caused 389 of 583 episodes (66.7%). Resistance to ampicillin or tetracycline was noted in 57% of all Shigella isolates, and 82% were resistant to cotrimoxazole. It is concluded that shigellosis is highly endemic in southern Israel, resistance to antimicrobial drugs is common and living conditions of the population influence the seasonal occurrence of the disease and select for morbidity with specific organisms.