Over a 50-month period, 4,508 stool specimens from patients with diarrhoea were bacteriologically examined at the National University Hospital, Singapore. Salmonella serotypes other than the typhoid and paratyphoid bacilli were the most common finding, being isolated in 10.8% of cases. Campylobacter jejuni was unexpectedly infrequent (1.9%); Aeromonas hydrophila was found in 1.8%. No other aerobic pathogen occurred in more than 1% of cases. Clostridium difficile was sought only when requested, and was isolated from 9.6% of cases tested. Testing for enteropathogenic Escherichia coli was limited to children under 1 year old. Gentamicin was active against the greatest number of aerobic isolates, followed by chloramphenicol and cotrimoxazole. The C. difficile isolates were all sensitive to metronidazole.