Introduction: For transurethral urologic surgery floor drainage is necessary for disposal of large amounts of fluid; for skin incision surgery floor drainage is unnecessary. The presence of floor drainage in an operating theatre may have a negative impact on the surgical site infection (SSI) rate after skin incision surgery due to aerosol contamination. We examined whether multifunctional use of an operating theatre would increase the SSI rate after skin incision surgery. Patients and Methods: Patients undergoing skin incision surgery on the kidney or prostate were prospectively divided into two groups with regard to operating theatre equipment. 272 patients were operated on in a theatre with floor drainage and 755 patients were operated on in a theatre without floor drainage. SSIs were categorized using the CDC classification and SSI rates in the two different theatres were determined. Results: No statistically significant difference (p = 0.86) in SSI rates after kidney and prostate surgery was found for operations in theatres with (2.6%) and without floor drainage (2.8%). Conclusions: Multifunctional use of an operating theatre with floor drainage for transurethral and skin incision surgery does not increase SSI rates. Thus, multifunctional use of theatres with floor drainage might lead to a gain in flexibility in the use of operating theatre capacity.