A multicenter randomized study was conducted to compare the efficacy and safety of ofloxacin with that of trimethoprim/sulfamethoxazole (TMP/SMX) in the treatment of uncomplicated urinary tract infection in adults. Patients were randomized to receive either oral ofloxacin 200 mg daily for three days (102 patients), or oral TMP/SMX 160 mg/800 mg twice daily for seven days (100 patients). The pathogen was eradicated in 73 (97.3%) of the 75 evaluable patients receiving ofloxacin and in 66 (97.1%) of the 68 evaluable patients receiving TMP/SMX. The most frequently isolated pathogens were Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. More urinary pathogens were susceptible to ofloxacin than to TMP/SMX, although this difference was not statistically significant. The clinical cure rate for patients receiving ofloxacin was 93.3%, with 4% improved and 2.7% failed. For patients receiving TMP/SMX, the clinical cure rate was 86.4%, with 12.1% improved and 1.5% failed. Side effects were reported by 29.7% of the patients receiving ofloxacin and by 40.4% of the patients receiving TMP/SMX. Drug-related adverse experiences, as determined by the investigators, occurred in 5% of the ofloxacin patients and in 15.2% of the TMP/SMX patients, a statistically significant difference. No patients receiving ofloxacin, compared with three patients receiving TMP/SMX, discontinued therapy because of an adverse reaction. These results indicate that short-course ofloxacin is as effective as TMP/SMX in the treatment of uncomplicated urinary tract infection. Ofloxacin therapy is also better tolerated than TMP/SMX.