During December 1995-February 1996, four cases of a bacteremic illness (three accompanied by cellulitis and the fourth with infective endocarditis, meningitis, and probable septic arthritis) were identified among patients at a hospital in Ontario. Streptococcus iniae, a fish pathogen not previously reported as a cause of illness in humans, was isolated from all four patients. All four patients were of Chinese descent had a history of preparing fresh, whole fish; three patients for whom information was available had had an injury associated with preparation of fresh, whole fish purchased locally. This report summarizes information about these cases and presents preliminary findings of an ongoing investigation by health officials in Canada, which suggests that S. iniae may be an emerging pathogen associated with injury while preparing fresh aquacultured fish.