Clostridium difficile and/or toxin B were isolated from the faeces of 3 (1.6%) of 184 patients within the first two days of hospitalisation in the University of Tübingen, Gynaecological Clinic. With following stool samples from a total of 117 patients the isolation rate of C. difficile was examined in relation to the treatment with antibiotics. From the first group of 61 patients, who had had gynaecological operations and were not treated with any antibiotic, the isolation rate of C. difficile rose statistically but not significantly from 0% at the time of admission up to 3.3% during hospitalisation. Amongst the second group of 17 patients, who had had gynaecological operations and were treated with various antibiotics for at least three days, the isolation rate was also found to rise insignificantly from 0 to 11.8% (p < 0.1). The third group of 33 patients, who had had gynaecological operations and perioperative prophylaxis with cefoxitin (one to three doses 2 g each), the isolation rate rose significantly from 0 to 12.1% (p < 0.05). The result of this study shows that the bacterial flora of the gut was probably altered even after a very brief application of cefoxitin. In two environmental examinations on the wards of the patients of this study, C. difficile was not isolated in any case.