Sixty cases of primary MALT type lymphomas were subjected to a retrospective analysis, which assessed the proliferative (PI) and apoptotic (AI) indices. The MIB-1 antibody was used for the Ki-67 proliferative antigen epitope, as well as the Apoptag In Situ Apoptosis Detection Kit (Oncor). The group included 32 low-grade and 28 high-grade lymphomas. In addition, the high-grade lymphomas group was divided into subgroups, depending on the presence or absence of a low-grade component. Significant differences were demonstrated in proliferative and apoptotic indices for cases differing with respect to their histological grade and stage. In low-grade lymphomas, the increase of AI value was associated with the increase of blast cells in the neoplastic infiltrate. It was necessary to exclude from this group cases of intensified plasmocytic differentiation, as such intensified differentiation alone was associated with increased AI values also. Considerable variations were noted in AI and PI values, even in groups with the same histological grade. The results suggest a potential clinical importance of AI and PI evaluations, stressing the necessity of treating each case of primary MALT type lymphoma individually. It appears that histological grade and stage evaluation alone may be insufficient when planning the management and prognosticating the response to therapy.