Acute thrombocytopenia developed in a 27-year-old woman with systemic lupus erythematosus (SLE). Antibodies to red cells and granulocytes were identified in addition to an increase in platelet-associated IgG. Serum complement levels were reduced, circulating immune complexes were present, and high titers of antinuclear antibodies and antibodies to native DNA were demonstrated. Attempts to aspirate bone marrow were unsuccessful due to an increase in marrow reticulin. Treatment with corticosteroids reversed the thrombocytopenia but not the myelofibrosis or the serologic abnormalities. A review of the literature revealed four other patients, two men and two women, with SLE and myelofibrosis. In two of these patients, the myelofibrosis regressed following therapy with corticosteroids.