Chronic bacterial prostatitis (CBP), which is characterised by recurrent urinary tract infection (UTI) and persistence of pathogenic bacteria and evidence of inflammation in the prostatic secretions, is one of the most common causes of relapsing UTI in men. In this study, we evaluated the antimicrobial and anti-inflammatory effects of garlic as well as the synergistic effect of garlic with ciprofloxacin on the treatment of CBP in an animal model. An experimental CBP model was induced in 60 adult male Sprague-Dawley rats by instillation of 0.2 mL of bacterial suspension (Escherichia coli Z17, O2:K1:H-) containing 1 x 10(8) colony-forming units/mL into the prostatic urethra. Microbiologically and histologically proven CBP was demonstrated in 68.3% (41/60) of the rats after 4 weeks of bacterial instillation. The 41 rats demonstrating CBP were randomly divided into four treatment groups: control; garlic; ciprofloxacin; and garlic plus ciprofloxacin. After 3 weeks of treatment, microbiological cultures of the urine and prostate samples as well as histological findings of the prostate were analysed. Microbiological cultures and histological findings of the prostate samples demonstrated reduced bacterial growth and improved inflammatory responses in all three experimental groups compared with the control group. The garlic group showed a statistically significant decrease in bacterial growth and improvement in prostatic inflammation compared with the control group. The garlic plus ciprofloxacin group showed a statistically significant decrease in bacterial growth and improvement in prostatic inflammation compared with the ciprofloxacin group. These results suggest that garlic may have anti-inflammatory and antimicrobial effects as well as a synergistic effect with ciprofloxacin. We therefore suggest that the combination of garlic and ciprofloxacin may be effective in treating CBP with a higher success rate.