Intravascular malignant lymphomatosis (IML) is a rare form of extranodal non-Hodgkin lymphoma characterized by proliferation of malignant lymphoid cells within the lumen of small blood vessels. We describe a case of IML presenting with non-specific pulmonary symptoms, weight loss, intermittent fever and a confusing collection of laboratory findings. Later on the patient developed cardiac symptoms, and finally diffuse cerebral symptoms and skin lesions. His condition deteriorated and he died within six months. The diagnosis of IML was made at autopsy. Complete remission and long-term disease-free survival may be obtained with standard chemotherapy directed at high-grade lymphomas. It is important to remember IML in the differential diagnosis of patients with confusing and changing ischaemic symptoms and signs from several organs.