A total of 16 men suffering from refractory chronic bacterial prostatitis caused by Escherichia coli was treated with ciprofloxacin for 4 weeks. After a median followup of 30 months (range 21 to 36 months) 10 of the 16 patients were considered cured as judged by bacteriological results and clinical symptoms. In 2 men a second ciprofloxacin regimen obviously showed success also. In 2 patients ciprofloxacin therapy failed and in 2 therapy had to be discontinued due to side effects of the central nervous system.