We studied 21 bone marrow specimens from 21 patients with systemic lupus erythematosus (SLE) and peripheral cytopenias: anaemia (Hb < 10 g/dl), and/or leucopenia (white blood cell count < 4 x 10(9)/l), and/or thrombocytopenia (platelets < 150 x 10(9)/l). None of the patients had used immunosuppressive drugs in the 2 months before the study, and 11 (52.4%) had never used these drugs. The global and specific series cellularity, degree of fibrosis and necrosis were evaluated by bone marrow trephine; morphological abnormalities and iron stores were evaluated by cytological smears. The most important abnormalities viewed in bone marrow biopsies were: global hypocellularity (47.6%), increased reticulin proliferation (76.2%) with myelofibrosis in one patient, and necrosis (19.0%). The marrow aspirates were difficult to obtain in four patients, who showed an increased reticulin proliferation on histological analysis. Plasmocytosis was present in 26.7% of cases and in one there was a serum monoclonal component (IgG kappa). Iron stores were normal or increased in 26.7% of specimens and decreased or absent in 73.3%. The most frequent peripheral abnormality was leucopenia in 90.4% (19/21) and granulocytic hypoplasia was observed in 47.3% (9/19) of these patients. We conclude that the bone marrow may be a target organ in SLE with cytopenias.