Angiogenesis is increased in hematologic malignancies, including non-Hodgkin lymphoma (NHL). Elevated serum levels of two important angiogenic factors, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), are associated with a poor prognosis. Immunohistochemistry was used to evaluate 27 patients with NHL and bone marrow involvement (17 with low-grade B-cell NHL, including 7 with higher grade transformation; 6 with intermediate-grade B-cell NHL; and 4 with T-cell lymphoma). Among the 17 patients with low-grade B-cell NHL, results for 7 were positive for VEGF stain (41.2%), and results were negative for all other stains for VEGF receptors, bFGF, and bFGF receptors. In the 10 patients with intermediate-grade B-cell NHL and T-cell lymphoma, all VEGF staining was positive (100%), but bFGF staining was only weakly positive in 2. Staining results for seven patients who had low-grade B-cell NHL with higher grade transformation showed that VEGF staining was positive in large lymphoid cells of 5 patients and in small lymphoid cells of one patient. Staining for the receptors VEGFR-1 and VEGFR-2 was positive in large lymphoid cells in four and two cases, respectively. Staining for bFGF was positive in two cases of large lymphoid cells. We concluded that VEGF, but not bFGF, was associated with higher tumor grading of NHL and high-grade transformation of low-grade lymphoma.