A double-blind comparative study of S6472 and cefaclor (CCL) was conducted to evaluate the therapeutic efficacy, safety and usefulness in the treatment of skin and soft tissue infections. Either 750 mg b.i.d. of S6472 or 750 mg t.i.d. of CCL was administered orally to patients for a period of 7 consecutive days. Of the 250 cases (123 cases of S6472 group and 127 cases of CCL group) recruited in this trial, 228 cases (114 cases of S6472 and 114 cases of CCL) were adopted by the committee members for the evaluation of therapeutic efficacy, 238 cases (118 cases of S6472 group and 120 cases of CCL group) for usefulness, and 245 cases (121 cases of S6472 group and 124 cases of CCL group) were adopted for the evaluation of side effects. The backgrounds of both patients group were almost similar. The results obtained were as follows: Overall clinical effectiveness Of the 114 patients treated with S6472, excellent clinical responses were obtained in 11 patients, good in 79, fair in 19, poor in 5 (efficacy rate 78.9%), and of the 114 patients treated with CCL, excellent were in 16, good in 78, fair in 13, poor in 7 (efficacy rate 82.5%). There was no statistically significant difference between the 2 groups. Clinical effectiveness classified by initial severity and bacteriological efficacy There was no significant difference between the 2 groups in the clinical effectiveness classified by initial severity and in the bacteriological efficacy. Side effects were noticed in 5 patients of 121 treated with S6472 (4.1%) and in 2 patients of 124 treated with CCL (1.6%), and other 13 patients developed some abnormal laboratory findings. But these undesirable reactions were mild, and developed no significant difference between the 2 groups in the incidence of side effects. There was no significant difference between the 2 groups in the usefulness of the drugs. Conclusively, 750 mg b.i.d. of S6472 is anticipative of the same clinical efficacy, safety and usefulness as compared with that of 750 mg t.i.d. of CCL in the treatment of skin and soft tissue infections.