A case of Ki-1 lymphoma suspected on the basis of aspiration cytology of cervical lymph nodes is reported. The patient was a 43-year-old male with the chief complaint of a rapdily growing rt cervical mass. Aspiration cytology revealed large tumor cells with multinucleated giant cells, which were similar to those in non-Hodgkin lymphoma, large cell type. The nuclei were mostly round-shaped, but some were convoluted or ring-shaped. Ki-1 lymphoma was suggested by the presence of characteristic ring-shaped nuclei. The giant cells looked like Reed-Sternberg cells, but differed in that the chromatin pattern was rougher with darker appearance of the nucleus and smaller nucleoli. The cytoplasm was basophilic and vacuolated, and some cells were even filled with large vacuoles, thought to be a characteristic cytoplasmic feature of Ki-1 lymphoma. Erythrophagia was also seen in some cells. Acid phosphatase showed stronger activity than in T cell lymphoma or Reed-Sternberg cells, but was weaker than that of histiocytes. Immunocytochemical staining was positive for Ki-1, EMA, HLA-DR, IL-2 R and was partially positive for LCA, MT-1, UCHL-1. No monoclonality was observed based on rearrangement of immunoglobulins and T cell genes. The above mentioned characteristic features of the tumor cell and confirmation by immunocytological staining were crucial in the diagnosis of this disease.