Ten patients were treated, most of pre-school age, with acute osteomyelitis, produced by Staphylococcus aureus and Salmonella, having evolved for approximately one week, with sodium cephazolin at doses of 60 mg/kg/day intramuscularly in two daily injections for the first seven days and then in a single dose every twenty-four hours for four to seven weeks. Nine of ten patients were asymptomatic six months after this treatment. The patient who manifested chronic signs at the end of six weeks of therapy continued to be treated with three weekly injections of the same drug at an equal dose until the completion of six months, at the end of which he was asymptomatic. Ten patients with chronic osteomyelitis having evolved for two months to five years, due to penicillin-resistant Staphylococcus aureus, were treated with cephapirin at the dose of 30 mg/kg in one daily injection intramuscularly for three to four weeks and then the same dose on Mondays, Wednesdays and Fridays until the completion of six months. Eight patients who required it were sequestrectomized. Seven of the ten patients improve and remained asymptomatic for the same period of observation. The three patients who did not show marked clinical improvement did exhibit an appreciable radiological recovery. We have presented these regimens of treatment with a view of encouraging research into the intermittent administration of bactericidal antibiotics for pyogenic infections; in spite of the good results, we do not dare to recommend them in daily practice.