Twenty patients undergoing orthopaedic surgery for total hip replacement received a single prophylactic intravenous dose of 2.2 g Augmentin (2 g amoxycillin + 200 mg clavulanate). Bone samples removed during the operation were saved for amoxycillin and clavulanate assay. The proportion of inorganic matter in the bone samples was determined to calculate the concentrations of the drugs in their distribution volume. The cortical and cancellous bone were penetrated to a comparable extent by both compounds yielding maximum concentrations at one hour after the end of the infusion. The mean concentrations of amoxycillin in the cortex and spongy layer were 26.0 and 18.2 mg/kg within 1 h, 23.8 and 19.8 mg/kg in the interval from 1 to 2 h after infusion, and 9.2 and 5.9 mg/kg between 2 and 5 h. The corresponding values for clavulanate were 2.3 and 1.6 mg/kg, 2.5 and 1.6 mg/kg, and 1.0 and 0.7 mg/kg, respectively. No postoperative wound infections occurred in these patients.