Salmonella was the most frequent bacterial pathogen isolated from patients with acute diarrhoea in Hong Kong. In Queen Mary Hospital, the major hospital on Hong Kong Island, 94.7% of salmonellae isolated from faecal specimens from patients during the period 1973-82 belonged to the gastroenteric group, while 5.3% belonged to the enteric fever group. Amongst the gastroenteric group, 68 salmonella serotypes were identified, with Salmonella derby, S. typhimurium and S. anatum being the predominant ones. Three outbreaks caused by S. johannesburg, S. worthington and S. wandsworth were detected. Of S. typhimurium, 61.6% were resistant to multiple antibiotics and belonged to four major phage types: 193, 22, 138 and U288. The majority (96.8%) of S. johannesburg strains which caused a widespread epidemic were multiply-resistant. Multiple antibiotic resistance was rarely observed in most other gastroenteric salmonellae. S. typhi was the commonest of the enteric fever group isolated from the blood of patients. Nineteen phage types were identified; E1 being the commonest (18.5%) while 21% were nontypable. Many of these isolated were resistant to streptomycin or sulphadiazine, but none were resistant to ampicillin, chloramphenicol or trimethoprim.