A model of intracerebral hematoma that closely resembles the state in humans after spontaneous intracerebral hematoma was developed. Sequential changes in experimental intracerebral hematomas were compared with the in vivo findings in spontaneous intracerebral hemorrhage. The clinical series consisted of 28 patients with spontaneous intracerebral hemorrhage observed by CT during their natural course from 1976 through 1978. The experimental series consisted of 26 adult mongrel dogs with intracerebral hematoma near the basal ganglia studied by CT and histological examinations. In neither the clinical nor the experimental series was the time of decrease in density beginning in the periphery of the hematoma or the first appearance of ring enhancement and its concentric concentration toward the center of the hematoma affected by the size of the hematoma. In the experimental series, the tissue reaction near the periphery of the intracerebral hematoma showed constant processes: First, a necrotic layer appeared; ...