Worldwide data show that there is increasing resistance among urinary tract pathogens to conventional drugs. The aim of this study was to obtain data on susceptibility patterns of pathogens responsible for urinary tract infections (UTIs) in Poland to currently used antimicrobial agents. A multicentre study of 141 pathogens from hospital-acquired infections and 460 pathogens from community-acquired infections was carried out between July 1998 and May 1999. The most prevalent aetiological agent was Escherichia coli (73.0%), followed by Proteus spp. (8.9%) and other species of Enterobacteriaceae (9.6%). Few community infections were caused by Gram-positive bacteria (2.2%). Gram-positive cocci were isolated more frequently from a hospital setting (14.1%) and the most common were Enterococcus spp. (8.5%). Pseudomonas aeruginosa was found only among hospital isolates and was responsible for 10.7% of infections. E. coli isolates from both community and hospital infections were highly susceptible to many antimicrobial agents with the exception of those isolates producing extended-spectrum beta-lactamases (ESBLs). Of all Enterobacteriaceae tested, 38 strains (6.9%) were capable of producing ESBLs.