1. The dominant role of pathogenic staphylococci in surgical infections has been confirmed by positive isolations in 89·9 per cent of a wide variety of lesions in a hospital infective unit. Of 150 staphylococci isolated, 147 were sensitive to fusidic acid, two were slightly sensitive and only one was resistant.

2. Fusidic acid was administered as sodium fusidate to 100 patients with staphylococcal infections (including seventy-two with chronic post-traumatic osteomyelitis). Sterile swabs were achieved in seventy-seven of these patients and in the remaining twenty-three a change of flora was detected.

3. Bone samples were taken at operation from twenty-nine patients with chronic osteomyelitis who had been treated for at least five days with fusidic acid. Depending on dosage, the mean fusidic acid concentrations were 7·3 and 9·8 micrograms per gram. Corresponding levels in non-inflammatory bone samples from thirty-one patients were, depending on the duration of treatment, 12·3, 2l·3 and 25·4 micrograms per gram. The fusidic acid levels in cancellous bone were almost twice as high as those in compact bone.

4. The relevance of these findings to the use of fusidic acid therapy as an adjunct to surgical management of chronic osteomyelitis is discussed.