Objective: to evaluate the hematological involvement (HI) in hospitalized patients with juvenile systemic lupus erythematosus (JSLE). Methods: from 1994 to 2005, 195 admissions occurred in 77 JSLE patients (American College of Rheumatology criteria) and were followed by the Pediatric Rheumatology Unit of the Instituto da Criança-University of São Paulo. These admissions were evaluated according to the presence of HI at onset or during the evolution of the disease: autoimmune hemolytic anemia (AHA) or thrombocytopenic purpura. All patients performed at least two complete blood counts. AHA was defined by a fall in hemoglobin levels (beyond 2 g/dl), reticulocytosis, increase in lactate dehydrogenase (LDH) and indirect bilirubin levels, and a positive Coombs test. The hematologic manifestations associated with infection, neoplasia and aplastic anemia were excluded. Results: HI occurred in 14 patients (18.9%), with 15 admissions. Among these patients, 11 were female, 7 had trombocytopenic purpura, 5 AHA and 2 Evans syndrome. HI as onset and single manifestation of JSLE was observed in three patients. All the patients with trombocytopenic purpura presented cutaneous bleeding (petechia and/or ecchymosis). All had disease activity and simultaneously presented other manifestations of JSLE, particularly nephritis and vasculitis. Initially, all patients received pulsetherapy with methylprednisolone and prednisone later. In three patients the treatment aimed predominantly the control of hematologic manifestations, with intravenous gammaglobulin. The most used immunossupressive therapies were intravenous cyclophosphamide, cyclosporine and azathioprine. One patient died of central nervous system bleeding. No patient needed splenectomy. Conclusions: isolated HI was a severe manifestation in hospitalized patients with JSLE, generally associated with an active and systemic disease.