The tumor necrosis factor (TNF) is a pro-inflammatory cytokine involved in the severity of different immune-regulated diseases including autoimmune, infectious, and malignant diseases. Chronic immune system stimulation could be a potential etiologic factor in these diseases. Given the determining role of TNF acting early in the immune response, we investigated the effect of an inherited genetic polymorphism at TNF promoter (-308A/G) on a predisposition to non-Hodgkin's lymphoma (NHL). The genotype distribution was determined in 194 patients with NHL and 160 age- and sex-matched population-based controls. The comparison of the -308TNF genotypes between the NHL patients and the controls showed a significant excess of A/A genotype that is previously associated with higher TNF production. Indeed, the A/A genotype is present in 7.7% of the cases, but in only 2.5% of the controls. This genotype is associated with a significant increased risk of NHL (odds ratio = 3.63, P = 0.028). These results indicate that the genetic polymorphism which could lead to an increased TNF production or a neighboring gene within the MHC region may influence the susceptibility to NHL in Tunisian population. Other epidemiologic studies carried out in both the Tunisian population and elsewhere are needed to confirm this finding.