Several reports have shown that the degree of positivity for the AgNOR count can be used to evaluate the aggressiveness of malignancies since it express an increased protein-synthesis activity. This technique was applied to six cases of stage I osseous non-Hodgkin's lymphoma--4 intermediate grade (2 diffuse small, non-cleaved cell and 2 diffuse large, non-cleaved cell lymphomas) and 2 high-grade immunoblastic lymphomas--in order to assess the histologic grade and the number of AgNOR-positive regions. It was noted that survival together with the trend to invade the surrounding soft tissues (i.e., the tumour aggressiveness) correlated with the AgNOR granule count. Both factors were also related with Ki-67 cell-proliferation antibody positivity. Such correlations were even higher than those found with the histologic features conventionally evaluated in the Working Formulation, so they seem to convey more reliable indices of neoplastic growth potential.