Leukemic reticuloendotheliosis is increasingly noted to have a spectrum of laboratory findings suggestive of both lymphocytes and monocytes. However, previous reports have not noted a clinical presentation which may be confused with lymphoma. This report documents a case of leukemic reticuloendotheliosis in a 29 year old man with clinical findings of diffuse lymphadenopathy, organomegaly and cutaneous involvement. As cytotoxic agents may be dysfunctional in leukemic reticuloendotheliosis, the ability to distinguish between the disorder and a lymphomatous process may be critical to the patient's management. Both morphologic examination of the "hairy-cell" and cytochemistry may not give an unequivocal differentiation between these two diseases. However, functional studies of the neoplastic cell, such as cell-marker analysis, phagocytic function and ultrastructural morphology, can define by noninvasive methods the correct diagnosis in the atypical presentation of leukemic reticuloendotheliosis.