A case of IgA multiple myeloma associated with myelofibrosis and radiological evidence of diffuse osteosclerosis from the disease onset is reported. Bone marrow trephine biopsies performed before and after chemotherapy treatment for myeloma showed grade 4 collagen fibrosis of the bone marrow, thickened bony trabeculae and the presence of plasma cells, both mature and immature. Serum electrophoresis revealed an IgA λ-paraprotein. Throughout the course of the disease, there was persistent radiological evidence of osteosclerosis, although several lytic lesions appeared late in the disease process. The patient died 5 years after presentation, during an episode of septicaemic shock. It is speculated that cytokine(s) released by the neoplastic plasma cells may stimulate a fibroblastic reaction within the marrow, which subsequently undergoes bony metaplasia resulting in osteosclerosis.