AIM Little is known about the significance of angiogenesis in the bone marrow of HIV-positive patients with myelodysplastic features (MDF). However, this process has been associated with the pathogenesis of primary myelodysplastic syndromes (MDS). The aim of the study was to investigate angiogenesis in the bone marrow of HIV-positive patients. METHODS Bone marrow biopsies from 28 HIV-positive patients were immunostained for factor VIII and the microvessel density (MVD) was quantitatively evaluated and compared with that of 32 biopsies from patients with primary MDS and to 18 control bone marrows from patients with no evidence of bone marrow disease. RESULTS Bone marrow MVD in HIV-positive patients was similar to that of MDS. However, both groups revealed significantly higher MVD counts compared to those of control bone marrows (MDF vs controls P=0.022, MDS vs controls P=0.001). CONCLUSIONS Bone marrow from HIV-positive patients with MDF reveals similar microvessel counts compared to those with primary MDS, although both differ significantly from that of control bone marrow. Elucidation of the mechanisms underlying bone marrow angiogenesis in HIV-positive patients, may provide further insights into the pathobiology of AIDS and might be of value for the development of new therapeutic strategies for this disease.