Over the last 10 years the treatment of choice for urinary tract infections (UTIs) in Turkey has changed from co-trimoxazole to quinolones owing to the rate of resistance to co-trimoxazole and its high level of therapeutic failure. The resistance ratio of 1939 UTI Escherichia coli from outpatients (1994-2003) was evaluated by Kirby-Bauer disc diffusion method for the aforementioned antibiotics to determine the change in resistance. The co-trimoxazole resistance ratio decreased during this period, with the highest ratio in 1996 (69.3%) and the lowest ratio in 2003 (38.5%) (P < 0.001). The lowest resistance ratios occurred in 1995 (4.1%) for ofloxacin and in 1996 (5.2%) for ciprofloxacin, and the highest resistance ratios occurred in 2002 (25.3% and 27.6%) for ofloxacin and ciprofloxacin, respectively (P < 0.00 1, P < 0.001). These findings emphasise that antibiotic usage policies, especially empirical therapies, should be based on antimicrobial resistance surveillance studies. (c) 2005 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.