The aim of this study is to present a histopathologic and immunohistochemical analysis of primary gastric lymphomas which were reclassified according to the concept of mucosa associated lymphoid tissue (MALT). The resected specimens from 41 patients with primary gastric lymphoma were investigated retrospectively. Immunohistochemical study was done to analyze the immunophenotype and bcl-2 and p53 proteins expression. Twenty three of the cases had tumors mainly located in the antrum. Histologically, 12 were low grade and 20 were high grade B-cell lymphoma of MALT, 9 other B-cell nonHodgkin's lymphomas. Helicobacter pylori was identified in 72% of the cases. According to Musshoff's modification, most of the MALT lymphoma cases had stage I or II disease. There was significant difference between low and high grade cases, in respect to depth of invasion in gastric wall. Immunohistochemically, the neoplastic cells in all MALT lymphomas expressed B-cell phenotype. Bcl-2 protein was found to be expressed in 59% and p53 protein expression was detected in 72% of cases. Among the B-cell lymphoma of MALT, bcl-2 positivity decreased and p53 positivity increased significantly as the histological grade advanced. So, an inverse correlation was observed between the expression of bcl-2 and p53. In conclusion, most primary gastric lymphomas are low or high grade B-cell MALT lymphomas and appear to arise in MALT acquired as a reaction to Helicobacter pylori infection. Expression of bcl-2 and p53 in gastric lymphomas may be associated with transformation from low-grade to high-grade disease.