Postoperative renal dysfunction (PRD) is well-documented after cardiovascular surgery but there are only limited available data concerning major orthopedic surgery, although patients may have several risk factors prone to impair renal function. We designed an epidemiologic prospective study to assess the incidence of PRD after total hip arthroplasty (THA) and to determine risk factors. Were included in the study 755 patients scheduled for THA in a single centre, over a 14 months period. Thirty-one demographic, clinical and biological parameters were collected for each patient. PRD was defined by a value of glomerular filtration, determined by the Cockroft and Gault formula<or=60 ml/min per 1.73 m2, on the seventh postoperative day. Risk factors were determined by univariate and then multivariate analyses using a linear regression model. Pre- and postoperatively (POD7), respectively 22.4% and 31.4% of the patients, had a creatinine clearance less than 60 ml/min per 1.73 m2. Univariate analysis documented age, ASA score, diabetes mellitus, chronic hypertension, the use of diuretics and NSAID, anemia, and an increased value of plasma urea as risk factors. Risk factors documented by multivariate analysis were: preoperative creatinine clearance less than 60 ml/min per 1.73 m2, (OR: 5.8, 95% confidence interval: [1.6-8.1], p=0.0006), preoperative plasma urea greater than 7.49 mmol/l (2.1 [1.4-11.1], p=0.04), age above 70 years (1.8 [1.1-4.3], p=0.02), and duration of NSAID's treatment beyond 5 days (3.2 [1.4-7.1], p=0.02). PRD is common after THA and is prone to develop in aged patients with comorbidities. Duration of NSAID's administration should be limited in those patients.