Infection after total hip or knee arthroplasty is a major concern for the orthopedic surgeon. Because postoperative recovery in patients undergoing hip or knee replacement is always characterized by a shift in basal laboratory parameters, the value of the routine use of these parameters in the detection of this major complication is controversial. The aim of this study was to evaluate the physiological behavior of these parameters, the most reliable of which are C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and white blood cell count (WBC). The pattern of these parameters was observed for 60 days after surgery in 74 patients (48 males and 26 females) who underwent total hip or total knee arthroplasty. Mean age was 65.4 years. ESR reached a peak on day 5 and then decreased as much as 3-fold by day 60. CRP displayed even greater sensitivity with a peak level on day 3 followed by a rapid return to basal levels. WBC also peaked on day 1. No significant differences were found between total hip arthroplasty and total knee arthroplasty. Observation of the pattern of these parameters identifies any nonphysiological modifications and enables suitable measures to be adopted.