Angiogenesis is important in development, maintenance and progression of haematological malignancies. Some clinical observations have indicated that in non-Hodgkin's lymphoma (nHL) tumour microvessel density (MVD) may correlate with tumour staging and outcome. The aim of the study was to examine relationship between MVD as a parameter of tumour angiogenesis measured by expression of CD34 and the grade of nHL histological malignancy as determined by REAL classification. 40 lymph node samples of patients with newly diagnosed nHL (17 women, 23 men; aged 48-70 yrs, median age 64 yrs; stage III and IV) and treated at the Department of Haematology, Wrocław Medical University in 1999-2002 were fixed in 10% buffered formalin and embedded in paraffin. In all the studied cases, sections were incubated with antibodies against CD34. The slides were stained with hematoxylin and eosin and evaluated histopathologically. Patients were divided into two groups according to histological malignancy: indolent nHL (19 patients) and aggressive nHL (21 patients). Mean MVD measured by expression of CD34 in aggressive and indolent nHL groups amounted to 19.45 +/- 11.24 vessels/0.375 mm2 and 21.7 +/- 12.4 vessels/0.375 mm2, respectively. Statistical analysis of microvessel staining demonstrated no correlation between tumour MVD and grade of histological malignancy in lymph nodes of nHL patients. Nevertheless, angiogenesis observed in nHL provides rationale for use of angiogenesis inhibitors in lymphoma therapy.