In a clinical double-blind study on 198 patients with a urinary tract infection, no differences were found between comparable groups treated with either sulfadiazine (SD) 1,000 mg/trimethoprim (TM) 320 mg or sulfamethoxazole (SM) 1,600 mg/trimethoprim 320 g daily for 2 weeks. The favorable results were obtained according to the bacteriological control in 85 and 79%, respectively. Also the incidence of side effects was the same (22 and 24%, resp.). The number of cases within which the treatment had to be discontinued did not differ percentually, either (6.6 and 8.4%, resp.). Based on the bacteriological sensitivity tests and the clinical trial, the authors conclude that TM can be combined with SD as well as with SM. Pharmacokinetic advantages, like a lower protein-binding and a lesser metabolism, may even make SD more preferable.