• Leukemoid reactions occurred in 136 patients (3.8%) hospitalized with shigellosis in Bangladesh. Sixty-eight percent of the patients with leukemoid reactions were children less than 4 years old. When compared with patients without leukemoid reactions, the leukemoid reactions were significantly associated with children aged less than 10 years. The most common serotype of Shigella in the patients with leukemoid reactions was Shigella dysenteriae 1, isolated from 96 patients (71%), whereas the most common species in patients without leukemoid reactions was Shigella flexneri, isolated from 2,119 patients (62%). The case fatality rate in patients with leukemoid reactions was 21% compared with 7.4% in patients without leukemoid reactions. These findings indicated that in patients with shigellosis, the leukemoid reaction was significantly associated with young children, isolation of S dysenteriae 1, and increased case fatality rate.