In a single-blind, randomized study of multicentre trial design 343 hospitalized geriatric patients (median age 83 years) suffering from symptomatic urinary tract infections (UTI) were treated with either norfloxacin 200 mg twice daily or pivmecillinam 200 mg 3 times daily orally for 7 days to compare the clinical efficacy and safety of the antibiotics in the elderly. The pathogen was Escherichia coli in 56.7%, other gram-negative rods in 37.2% and gram-positive cocci in 6.1%. Up to 18 days after cessation of treatment the original pathogen was eradicated in 60.5% of the 114 who were assessable for the effect of norfloxacin therapy and in 36.5% of the 96 patients in the pivmecillinam group (p less than 0.001). Adverse drug reactions, mostly gastrointestinal disturbances, were noticed in single cases.