A 54 year old patient suffering from mycosis fungoides developed an immune complex disease with mixed cryoglobulinemia (type III) and pulmonary vasculitis, an association so far unreported. We believe that the pathogenesis could be ascribed to a T-cell imbalance (increase in OKT4+ cells with inversion of the OKT4/OKT8 ratio) and to a functional T-cell defect, as suggested by the reduced mitogenic responses to PHA and ConA we observed.