Cefpiramide (CPM) 2 g was preoperatively administered to 29 patients by intravenous drip infusion for 20 minutes. Concentrations of CPM in bone marrow blood, peripheral blood, and bone tissue were determined at 30, 60, 120, 180, 240 and 360 minutes after CPM administration. Mean concentrations of CPM in peripheral blood, bone marrow blood were peaked at 60 minutes after injection, those in bone tissues (cortex, cancellous bone) peaked at 30 minutes after injection. The mean ratio of the CPM concentration in bone marrow blood to peripheral blood was 105.5%, that in cortex (/g) to peripheral blood (/ml) was 17.7%, and that in cancellous bone (/g) to peripheral blood was 18.2%. These concentrations were maintained above MIC80 for 6 hours. From the above results, CPM appears useful for the prevention of infection in orthopaedic operation (skeletal surgery).