We present the long-term results of a protocol of empirical monotherapy of continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis with ciprofloxacin. One hundred and fifteen episodes of peritonitis were studied. The treatment protocol included 5 days of intraperitoneal (IP) administration of the drug, followed by 10 days of oral therapy. A good clinical response was obtained in 83% of the cases, while treatment failure was observed in 4% and relapse in 7%. A decrease in the sensitivity to ciprofloxacin of the peritonitis agents was observed in the study, with Staphylococcus spp. in particular. Three episodes of peritonitis due to bacteria resistant in vitro to ciprofloxacin responded to the treatment protocol. Ciprofloxacin attained good plasma levels both after oral and IP administration. However, dialysate levels were poor after oral administration. The most frequent side effect was gastric intolerance to oral ciprofloxacin. Two patients experienced severe adverse reactions to the drug. Ciprofloxacin may be a good choice for empirical monotherapy of CAPD-related peritonitis. However, the emergence of bacterial resistances must be carefully monitored. The drug should be administered intraperitoneally, at least to induce remission of the infection. Side effects are not frequent, but ciprofloxacin should not be considered an innocuous drug.