Recently immunophenotyping has become a valuable tool in the diagnostic workup of malignant lymphoma. We classified 79 consecutive cases of non-Hodgkin's lymphoma experienced at our hospital during the last two years according to the Working Formulation and immunologically using MT1, UCHL1 and MB2 monoclonal antibodies. The results of this study are as follows: 1) four cases (5.1%) were low grade, 54 cases (68.4%) were intermediate grade, and 21 cases (23.3%) were high grade. The most common subtype was 'diffuse, mixed' type, 2) fifty cases (63.3%) showed T-cell phenotype and 14 cases (17.7%) showed B-cell phenotype. Immunophenotyping was impossible in 15 cases due to either double staining or negative staining. 3) the incidence of extranodal presentation was high (65.8%) and the most common extranodal site was the upper aerodigestive tract (29.1%) followed by the gastrointestinal tract (16.4%), and 4) MT1, UCHL1 and MB2 monoclonal antibodies are valuable markers of T- and B-cells in paraffin embedded tissue, enabling retrospective study. However, because these antibodies are not lineage specific, the results of immunostaining should be interpreted with caution.