Interhemispheric subdural haematoma (ISH) is a rare complication of head injury with only 19 cases reported since 1940, but it may also occur spontaneously (three cases). In both circumstances, clotting disorders are frequent (six cases). We have recorded seven cases (five traumatic, two spontaneous).Classically ISH is due to tearing of bridging veins or cortical contusions. In one of our cases, it was due to arterial bleeding from a pericallosal branch. CT scan shows that ISH may extend above the tentorium and on the hemispheric convexity. Mortality is high (35%). The best operative procedure is parasagittal craniotomy. Chronic interhemispheric subdural haematomas also occur.