Clinical effects of combined use of aztreonam (AZT), amikacin (AMK) and clindamycin (CLDM) in 46 cases with infectious diseases in obstetrics and gynecology were retrospectively studied in 2 groups, and the following results were obtained. 1. No significant difference in efficacy rates was noted between AZT plus CLDM treated group (n = 25) and AMK plus CLDM treated group (n = 21) (96.0% vs. 95.2%), while rate of excellent efficacy was slightly higher in AZT plus CLDM group than AMK plus CLDM group (24.0% vs. 14.3%). 2. No significant difference in bacteriological clinical effects was also noted between the 2 groups, while bacteriological eradication rate was higher in the AZT plus CLDM group than in the other group (76.2% vs. 50.0%), and the difference was particularly clear in the eradication rates of aerobic, Gram-negative bacteria (88.9% vs. 30.0%). 3. Subjective and objective side effects, and abnormalities of clinical test results were not found in either group.