From 1940 to 1984, 19 cases of septic dural-sinus thrombosis have been diagnosed at the Massachusetts General Hospital, and some 136 cases have been reported from other institutions. Septic thrombosis most frequently involves the cavernous sinuses (96 cases). Facial or sphenoid air sinus infection often precede cavernous-sinus disease. In addition to the classical signs of proptosis, chemosis, and oculomotor paralysis, isolated sixth-nerve palsy and hypo- or hyperesthesia of the fifth nerve may be found. The major pathogens associated with cavernous-sinus infection include Staphylococcus aureus, other gram-positive organisms, and anaerobes. Septic lateral-sinus thrombosis (64 cases) is almost exclusively a complication of otitis media and/or mastoid infection. Organisms causing this infection include Proteus species, Escherichia coli, S. aureus, and anaerobes. Septic thrombosis of the superior sagittal sinus (23 cases) most frequently accompanies bacterial meningitis or air sinus infection. Causative organisms include Streptococcus pneumoniae, S. aureus, other streptococci, and Klebsiella species. Because septic dural-sinus thrombosis is rare, this disease is frequently misdiagnosed. Evaluation should include lumbar puncture, air sinus films, and computed tomographic scan with contrast. Other helpful diagnostic tests may include carotid angiography, and dynamic brain scan. Orbital venography is the most definitive study in cases of chronic cavernous-sinus thrombosis. Therapy should include intravenous antibiotics and early surgical drainage of purulent exudate in the air sinuses or mastoid regions. Retrospective analysis suggests that treatment with heparin may reduce mortality in carefully selected cases of septic cavernous-sinus thrombosis. Anticoagulation is not recommended in other forms of septic dural-sinus thrombosis. Mortality in the antibiotic-era remains high, particularly in patients with septic thrombosis of the cavernous (30%) and superior sagittal (78%) sinuses.