Intravascular angiotropic lymphoma (IVL) is a rare variant of non-Hodgkin's lymphoma. Diagnosis in most cases is only achieved at post-mortem. We present a patient with pyrexia of unknown origin diagnosed with angiotropic lymphoma by bone marrow biopsy. We also review the limited published literature on associated chromosomal abnormalities. We provide further support for previously proposed non-random changes in IVL, namely, structural aberrations of chromosomes 1, 6 and 10, as well as identify further aberrations that may be non-random in chromosomes 4, 5 and 8, and postulate that the 6q21-24 region may be the site of a tumour suppressor gene. B-cell angiotropic lymphoma is a rare, but important, cause of pyrexia of unknown origin and we advocate that prolonged fever that has resisted diagnosis should prompt histological and immunocytochemical examination of bone marrow to facilitate rapid diagnosis and early institution of treatment.