The clinicopathologic and immunophenotypic findings of 25 cases of peripheral T-cell lymphoma in Korea were analysed. Seventeen cases (68%) of the 25 T-cell lymphomas presented in the extranodal sites including the nasal mucosa, tonsil, oral cavity, skin and rarely bone, mediastinum and breast. Immunologic studies showed that 12 cases (48%) of the lymphomas were of T-helper phenotype, 5 cases (20%) were of cytotoxic/suppressor phenotype, 1 case (4%) expressed both helper and cytotoxic/suppressor markers, and 7 cases (28%) lacked detectable markers for subsets. Histologically, fourteen cases (56%) showed histologic features suggestive of peripheral T-cell lymphoma. The more frequently seen histologic types by Working Formulation (WF) included large cell type and immunoblastic type. Classification by WF was straightforward in most cases of large cell, immunoblastic type. However, with some cases of small cell, large cell and mixed types, there were problems fitting the morphology seen into the WF category. We hope that the establishment of a world wide immunologic and clinicopathologic classification for peripheral T-cell lymphoma will be made in the near future.