One hundred and four dogs with clinical signs of urinary tract infection were selected by 15 practitioners in a multicentric, controlled and randomised study. The clinical diagnosis was confirmed by urinalysis and imaging. Each dog received either marbofloxacin (2 mg/kg orally once daily or 4 mg/kg by subcutaneous injection every four days) or amoxicillin-clavulanic acid tablets (12.5 mg/kg twice daily) for 10 or 28 days, depending on the clinical diagnosis. Rectal temperature, general condition, appetite, urinary signs, defecation disorders and pain on abdominal palpation were monitored at each visit, the timetable depending on diagnosis: three urinalyses and at least three examinations per case were performed. Side effects were also thoroughly sought at each examination. Marbofloxacin and amoxicillin-clavulanic acid both yielded good bacteriological cure rates (96.2 per cent versus 85.0 per cent, respectively) and clinical cure rates (83.3 per cent versus 69.7 per cent). Fewer relapses were observed in those dogs that received marbofloxacin. Few mild side effects were recorded with both products.