To develop guidelines for community health workers in the treatment of patients with diarrhoea, diarrhoea prevalence was actively surveyed for a year in a remote rural community of 915,000 persons, and the enteric pathogens and clinical features associated with diarrhoeal illness were determined in a sample of 300 patients. Bloody diarrhoea accounted for 39% of all diarrhoea episodes and 62% of diarrhoea-associated deaths. 51 (50%) of 101 patients with a history of bloody diarrhoea had Shigella infection, compared with 31 (16%) of 199 patients with other types of diarrhoea. A history of bloody diarrhoea was as predictive of the presence of shigella infection (positive predictive value 50%, negative predictive value 86%) as more complex prediction schemes incorporating other clinical features or stool microscopic examination. In the area of Bangladesh where the study was done reduction of diarrhoea-related morbidity and mortality will depend on control and treatment of shigellosis, and community health workers have been instructed to provide antibiotics for patients with a history of bloody dysentery.