We studied the clinical efficacy of oral treatment with ciprofloxacin (CPFX) alone and combined with clarithromycin (CAM) in patients with complicated urinary tract infection with or without an indwelling catheter. Patients were randomly allocated to 600 mg CPFX (CPFX group) or to 600 mg CPFX plus 600 mg CAM (combination group) for 14 days. Evaluation was done on day 14 according to the criteria advocated by the Japanese Urinary Tract Infection Committee. In patients with a urinary catheter, the combination achieved a higher complete bacterial elimination rate (50.0%) and clinical efficacy rate (83.9%) than CPFX alone (30.0 and 61.5%, respectively). While no significant difference was found in the bacterial elimination rate between the two groups, the clinical efficacy of the combination (40.0%) was superior to that of CPFX alone (23.3%) in patients with an indwelling catheter. The better clinical efficacy of the combination may partly be attributed to the antibiofilm effect of CAM in the clinical setting. The results also indicate that difficulties still remain in the treatment of complicated urinary tract infections in patients with an indwelling catheter.