Cefamandole penetration was studied in 32 normal bone specimens. No antibiotic bone binding was found. Blood contamination of bone samples was measured by the haemoglobin method. Mean corrected levels attained (5.8 μg/g) exceed MIC values of sensitive Staphylococcus aureus, Haemophylus influenzae and Enterobacteriaceae. Similar diffusion was observed in cortical and trabecular bone. The results obtained invite further studies on preoperative prophylaxis and treatment of osteomyelitis.