Results of trials of lomefloxacin (400 mg once daily) in elderly patients with uncomplicated urinary tract infections, complicated urinary tract infections, acute bacterial exacerbations of chronic bronchitis, and as prophylaxis for transurethral surgical procedures (400 mg single dose) have been analyzed. In patients greater than or equal to 65 years of age with uncomplicated urinary tract infections, the bacterial eradication rate for lomefloxacin was 100%. In patients with complicated urinary tract infections, the bacterial eradication rate for lomefloxacin (92.2%) was statistically superior to comparator agents (84.9%, p = 0.012). In elderly patients with acute exacerbations of chronic bronchitis caused predominantly by gram-negative pathogens, lomefloxacin eradicated 85.2% of pathogens versus 73.8% for amoxicillin (p = 0.004). Lomefloxacin was 98% effective as a prophylactic agent in transurethral surgery. The bacteriologic and clinical efficacy of lomefloxacin was similar in young and elderly groups of patients. Lomefloxacin appears to be as effective as the comparator drugs in both young and elderly patients.