A total of 89 patients, (>18 years), with symptoms of chronic prostatitis and inflammatory findings as well as the presence of Chlamydia trachomatis confirmed by DNA/RNA DIGENE hybridization method and/or by isolation, McCoy culture and Lugol stain in expressed prostatic secretion or in voided bladder urine collected immediately after prostatic massage, were examined. The patients were randomized to receive a total of 4.5 g of azithromycin for 3 weeks, given as a 3-day therapy of 1×500 mg weekly or ciprofloxacin 500 mg b.i.d. for 20 days. Patients’ sexual partners were treated at the same time. Clinical and bacteriological efficacy were evaluated 4–6 weeks after the end of therapy. Significantly higher eradication (36/45: 17/44; P=0.0002) and a significantly higher clinical cure (31/45: 15/44; P=0.0021) were achieved in the group of patients treated with azithromycin than in the ciprofloxacin group.