Natural killer (NK) cells are a third lymphocyte lineage, in addition to B- and T-cells, that mediate cytotoxicity without prior sensitization. NK cells also have phenotypic and genotypic characteristics; they express the NK-related antigen CD56 and T-cell markers such as CD2 and CD3 ϵ, but their T-cell receptor (TCR) locus is not rearranged. Non-Hodgkin’s lymphomas are divided into B- and T-cell neoplasms and NK-cell lymphomas. We describe 2 Japanese patients with nasal and nasal-type T/NK-cell lymphoma in which the skin, nasal/nasopharyngeal region, bone marrow, and lymph node were the sites of involvement. The clinical and histopathologic findings were recorded. In addition, immunophenotyping, TCR gene rearrangement, and the existence of Epstein-Barr virus (EBV) DNA by polymerase chain reaction amplification were determined. Clinically, the cutaneous eruptions were purplish, hard, multiple nodules. Histologically, angiocentric proliferation of small-to medium–sized, pleomorphic, lymphoid cells were observed. They revealed hand-mirror–shaped lymphocytes with azurophilic granules with the use of Giemsa staining by touch smear. These lymphocytes were found to be positive to immunophenotyping for CD2 (Leu5b), CD3 ϵ (DAKO), CD4 (Leu3a), and CD56 (Leu 19). No clonal rearrangement of TCR-β, -γ, and -δ genes and immunoglobulin gene markers were found, and no positive results of identification of EBV DNA were shown. The patients underwent cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy with complete remission; however, both had recurrence of disease. Because NK-cell lymphomas express some T-cell markers, they may be mistakenly diagnosed as peripheral T-cell lymphomas if they are not investigated for the NK-cell–specific marker, CD56. Therefore the importance of immunophenotypic investigations of CD56 should be stressed. Also, the importance of clinical investigation of nasal/nasopharyngeal lymphomas should be stressed when NK-cell lymphoma is diagnosed involving the skin, because NK-cell lymphomas are often associated with the nasal and nasopharyngeal region. (J Am Acad Dermatol 1999;40:850-6.)