We studied prospectively the incidence of symptomatic infections of presumed urinary tract origin requiring antimicrobial therapy among 54 male nursing home patients with chronic indwelling bladder catheters. During 514 patient-months at risk there were 106 episodes of symptomatic infection, for an incidence of 0.21 per patient-month at risk. Of the patients 80 per cent had at least 1 episode and 48 per cent had 2 or more. None of the clinical factors we examined, including age, nutritional status, stool incontinence, diabetes mellitus, episodes of catheter blockage and the use of chronic suppressant antimicrobial therapy, was associated with the development of symptomatic infection. Further research on host and pathogen-related factors that increase the risk for symptomatic infection, and improvements in infection control and catheter care protocols are necessary to decrease catheter-associated morbidity among male nursing home patients who must be managed by chronic indwelling catheterization.