Sections of surgical lymph-node biopsies of four types of malignant non-Hodgkin's lymphoma of B-cell origin (B-NHL) classified according to the R.E.A.L. terminology or lymphadenitis were immunostained in order to demonstrate endothelial CD34 (QBEnd 10) and to determine the microvascular density and vessel-size distribution using an interactive image-analysis technique. Only microvessels displaying a cross-sectional area corresponding to a diameter of between 3.2 and 34.6 μm were included. The intratumoral microvascular density (iMVD) was found to be significantly higher in chronic lymphatic leukaemia (CLL, n=13) compared with the clinically more aggressive mantle cell lymphoma (MCL, n=9) and diffuse large B-cell lymphoma (DLBCL, n=14). iMVD in CLL was also higher than in the follicular neoplastic parts (FL FOLL) of follicular lymphoma (FL, n=16). In FL FOLL the microvessel density was, moreover, significantly lower than in the surrounding non-neoplastic FL tissue. In lymphadenitis (LA, n=10) the iMVD was higher than in DLBCL, FL FOLL and MCL. The data suggest that future studies focusing on the relationship between iMVD and the clinical outcome within each particular NHL group should be carried out in order to verify whether iMVD is a prognostic factor in NHL, as it is in carcinomas.