Since 1963, the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), formerly the Cholera Research Laboratory, has maintained a field station in Matlab to treat patients from a surveillance population of 240,000 who have cholera and other diarrheal diseases. Since 1966, the authors have analyzed hospital records of 7141 surveillance-area patients culture-positive for v. cholerae 01 to relate the seasonality, age and sex distribution, and geographic trends with hypotheses concerning transmission, immunity, and risk groups. From this review, they have found that: 1) children 2-9 years old and adult women are most commonly hospitalized for cholera; 2) V. cholerae 01 emerges simultaneously throughout the area of surveillance, with the early cases being of different phage types; 3) three patients were hospitalized twice for cholera compared with 29 expected on the basis of life-table analysis (p less than 0.01), suggesting that immunity to severe disease conferred by previous illness may be stable and long-lasting; 4) no constant relationship was found between the times of onset or peaks of the yearly cholera epidemic and the times of onset or peaks of the monsoon rains or river water levels; and 5) an outbreak of multiply antibiotic-resistant V. cholerae 01 infection documented in 1979 raises questions about the dissemination of resistance plasmids, antibiotic-use patterns, and the need for other drugs in addition to tetracycline. While little progress has been made in understanding the mode of transmission of v. cholerae 01, and in identifying practices for prevention, fluid therapy in this area has decreased the case fatality rate significantly and provides guidance for similar programs elsewhere.