Tumor angiogenesis plays a significant role in cancer growth and metastasis. This complex process is influenced by a variety of angiogenic factors. Elevated serum levels or high expression of some of these factors have been shown to correlate with stage and prognosis in certain human malignancies. This has been demonstrated most consistently for vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). We tried to establish, whether pre-treatment serum levels of the angiogenic factors VEGF, bFGF, interleukin 8 (IL-8) and Flt3 ligand (Flt3L) correlate with prognostic variables in 30 patients with primary gastro-intestinal non-Hodgkin's lymphoma. Our results suggest that higher pretreatment serum levels of IL-8 and Flt3L are associated with higher stage (>or= II) and high grade, respectively. Elevated pretreatment serum levels of VEGF and bFGF were not associated with advanced disease characteristics and carried no prognostic information.