For the disease of the granular lymphocytes (GL) that contain azurophilic granules to proliferate in the peripheral blood, which is often complicated by anemia or neutropenia and which generally develop into chronic disease, the new designation of granular lymphocyte-proliferative disorders (GLPD) is being proposed. This disease include T-GL having CD3 antigen which forms a complex with T cell Ag receptor (TCR-alpha beta), and NK-GL which is CD3-negative but CD16- or NKH-1-positive, having non-MHC-restricted cytotoxicity. The two cases presented here demonstrate the characteristics of T-GL or NK-GL, however, while one case with NK-GL showed spontaneous decrease of GL, improvement of neutropenia and anemia without any treatment, the other case with T-GL became intractable and required repeated blood transfusion. On such differences in the clinical development of the disease, we have conducted investigations including a review of the literature to see whether there is any correlation between the characteristics of the proliferating cells and pathologic conditions of the disease, and whether this disease is indeed tumorous.