A multicenter study including 10 outpatient private laboratories (hospital laboratories excluded) was carried out in France. 1,611 urines samples from patients with UTI were collected during the forth trimester of 1987. The most frequently recovered pathogens were: E. coli (71%), Proteus mirabilis (9%), Staphylococcus coagulase (6%), Klebsiella (6%), Enterobacter (2%). Other sorts (Streptococcus D, Proteus sp, Pseudomonas aeruginosa, Enterobacter sp) were infrequent (less than 1%). The sensitivity of the aerobic Gram-negative bacteria to ampicillin, clavulanic acid-amoxicillin, cephalothin, gentamicin, pipemidic acid, norfloxacin and co-trimoxazole was tested.