A case is described in which the initial manifestation of a malignant lymphoma was an erythematous skin rash over the face, scalp and trunk. Immunological surface marker analysis showed the malignant cells to be of B lymphocyte origin with a homogeneous secretion of IgM-K. Repeated skin and lymph node biopsies and finally post mortem documented the progression of the lymphoma from that of a mixed lymphocytic-histiocytic type with a nodular pattern of growth to a diffuse histiocytic lymphoma with frequently bizarre cells. The theory of ecotaxis or homing of lymphocytes to the skin and other non-lymphoid organs of the body is discussed in an attempt to explain the occurrence of cutaneous involvement as a primary manifestation of lymphoma.