Three patients with acute spreading osteomyelitis of the skull complicating a frontal sinusitis are presented. The pathology and clinical features of this complication are discussed. Early rigorous antibiotic treatment accompanied by surgical intervention to drain purulent collections in the sinuses and scalp has been effective in controlling the disease. One patient required a craniectomy for removal of an area of chronic ostemoyelitis. The other two patients maintained on antibiotics for three months have shown no evidence of progression to chronic osteomyelitis and have remained free from relapse.