Twenty three Clostridium difficile strains isolated from diarrheic faecal samples of 22 patients in a neurosurgical department of the Pellegrin Hospital in Bordeaux between January 1984 and May 1987 (15 isolated in 1984, 2 in 1985, 3 in 1986 and 3 in 1987) and 15 strains isolated from 15 patients in other departments of the same hospital in 1984 have been compared using their antimicrobial susceptibility, cytotoxin production and electrophoretic pattern. Twelve of the 15 strains isolated in the neurosurgical department and 4 of the 15 strains isolated in other departments in 1984 were phenotypically identical. These findings suggest that the origin of C. difficile associated-diarrheas can be nosocomial.