Thirty five Bacteroides fragilis strains isolated from different, clinical specimens in 1976-1985 and in 1995, preserved in strains collection of Department of Clinical Bacteriology were studied. The cytotoxicity of 35 bacterial culture supernatants, were tested on the human carcinoma cell line HT29/C1. Two strains proved to be enterotoxigenic. One of those strains was isolated in 1985 from the human, before the existence of enterotoxin producing strain was reported. All 35 strains were metronidazol sensitive showing lack of correlation between enterotoxigenicity and metronidazol resistance.