A total of 27 patients, 21 of them females, with a median age of 56 were treated with pefloxacin for urinary tract infections. Some 74% of these infections were associated with upper tract symptoms, and Escherichia coli was the most common causative micro-organism (75% of cases). Fifteen patients had co-existent diseases with/without urological abnormalities. All strains of E coli were sensitive to pefloxacin; Actinobacter and one strain of Klebsiella and Streptococcus faecalis were resistant. Two patients who defaulted and one who had an initial negative bacterial culture were excluded from the analysis of the outcome. The overall bacteriological cure rate at four to eight weeks was 87.5% (21/24). The incidence of possible side-effects was high, occurring in 59% of the patients. Nausea, dizziness and vomiting were the most common. These were mild and did not require termination of treatment. Peripheral neuropathy, which disappeared four weeks after stopping pefloxacin, occurred in one patient.