This prospective study shows, that, neither an antibiotic prophylaxis of abacteriuric patients nor postoperative treatment of an asymptomatic urinary tract infection after transurethral prostatectomy have a significant influence on the clinical complications or the microbiologic results. After suprapubic prostatectomy complications in the control group were not significantly more frequent than in the group with antimicrobial prophylaxis. Patients with asymptomatic urinary tract infections before suprapubic prostatectomy had better clinical results, if they were treated with antibiotics as compared to a control group, although the difference control group was not significant. The correlation between consumption of antibiotics and development of resistant in pathogenic organisms forced us to use a more critical approach in the use of antimicrobial prophylaxis and therapy. This study shows clearly, that aseptic operations do not need an antibiotic protection and that faulty of asepsis cannot be corrected by antibiotics.