We describe a 27-month-old boy who was first admitted to our hospital on 7 January 1995 with nasal bleeding. From 6 months of age he has had lymphadenopathy, low levels of serum uric acid, increased levels of serum lactate dehydrogenase and hyper gamma-globulinemia. From the age of 18 months he has had persistent Epstein-Barr virus (EBV) infection (target cells; B cells), recurrent episodes of thrombocytopenia, anemia and hepatosplenomegaly. Dysmobility of the left leg and arm from a central nervous system complication during a relapse with pancytopenia on March 1995, was also observed. Relapses of thrombocytopenia with increases of platelet-associated immunoglobulin G and hepatosplenomegaly have been observed approximately every 2 months, and two relapses of pancytopenia were accompanied with weak positivity of Coombs test and low level of haptoglobin. These recurrent episodes were improved with prednisolone. However, now in June 1997 we have not been able to diagnose what underlies the above clinical symptoms, except that the patient has a persistent EBV infection.