One hundred patients, known to have been excreting Clostridium difficile cytotoxin in faeces, were reviewed retrospectively to determine the response time for treatment with oral metronidazole and vancomycin, and the effect of the additional administration of anti-motility agents. Records were available for 78 patients of whom 58 had received treatment with either metronidazole or vancomycin. Response and relapse rates were similar for the two treatment regimens. However, the mean duration of symptoms was significantly shorter in evaluable patients treated with vancomycin (3.0 days, n = 22) compared with those given metronidazole (4.6 days, n = 28) (Mann-Whitney-U, P < 0.01). No difference in the duration of symptoms, irrespective of antibiotic therapy, was associated with use of anti-motility agents. The increased cost of vancomycin compared with metronidazole for the treatment of C. difficile infection may be justifiable by reductions in the length of stay in hospital or in the need for nursing in isolation facilities, consequent upon a shorter symptomatic response time. Administration of anti-motility agents did not appear to impair response in patients with mild to moderate C. difficile infection.