The effectiveness of sodium fusidate and ofloxacin to eliminate nasal and catheter exit-site Staphylococcus aureus colonization and to prevent infections was compared in 31 patients on continuous ambulatory peritoneal dialysis (CAPD). In a prospective randomized study, 9 patients were treated with topical 2% sodium fusidate ointment applied in the anterior nares and in the pericatheter skin twice daily for 5 days; 9 subjects received oral ofloxacin 200 mg taken every 48 hours for 5 days and 13 subjects were in the control group. Treatment courses were repeated at one-month intervals. Mean duration of follow-up was 7.8 months (242 patients-month). Follow-up samples from the nares and the catheter exit-site were obtained every month from all participants to determine the presence of S. aureus. Development of S. aureus exit-site infection and peritonitis were assessed. During the study, S. aureus was recovered from 45%, 59% and 52% of the samples from the nares and/or exit-site in the sodium fusidate, ofloxacin and control groups, respectively (p = 0.13). S. aureus grew less frequently (p < 0.01) in samples from the exit-site in the sodium fusidate than in the other two groups. Eradication of nasal colonization (two negative cultures within one month) was observed in 43%, 40% and 33% of the cases in the sodium fusidate, ofloxacin and control groups, respectively (p > 0.50). The corresponding figures for exit-site eradication were 43%, 33% and 11%, respectively (p = 0.34). Twenty-four S. aureus-associated infection episodes (12 of exit-site and 12 of peritonitis) were diagnosed in 16 of the 31 patients.(ABSTRACT TRUNCATED AT 250 WORDS)