We report a case of venous thrombosis presented as ischemic intracranial expanding lesion localized in the parietal lobe of a young man with essential thrombocytosis. As surgical intervention became necessary we were able to investigate the morphological changes by histology and immunocytochemistry. The almost exclusive venous manifestation of thrombosis most probably initiated by elevated amounts of platelets suggests altered blood flow conditions as the predominant factor. Surgical interventions in such conditions are rare and might only proceed in space-occupying lesions with clinical symptoms. Treatment with inhibitors of platelet aggregation under strict control of the patient is the therapy of choice.