McKenna, Robert W., and Brunning, Richard D. Reed-Sternberg-like cells in nodular lymphoma involving the bone marrow. Am JClin Pathol 63: 779-785, 1975. Two patients with cells indistinguishable from Reed-Sternberg cells in bone marrow lesions of nodular poorly differentiated lymphocytic lymphoma are described. Both patients had lymph node biopsies showing nodular lymphoma. Bone marrow and blood involvement with the lymphoma was demonstrated at the time of initial diagnosis. Reed-Sternberg-like cells were not demonstrated in either case until later in the course of the disease, after the patients had been treated with numerous chemotherapeutic agents. Other similarities of bone marrow involvement with nodular lymphoma to Hodgkin's disease of the bone marrow are noted. The origin of the Reed-Sternberg-like cells in nodular lymphoma is not clear, but they could result from morphologicalteration of lymphoma cells by chemotherapy. The finding of Reed-Sternberg cells in bone marrow lesions should be interpreted with caution unless diagnostic biopsy material from other sites is available for study. (Key words: Bone marrow lymphoma' nodular lymphoma; Reed-Sternberg cells).