A 73-year-old man was admitted for investigation of pancytopenia. His physical examination was unremarkable and the bone marrow aspirate was compatible with myelodysplastic syndrome (RAEB). Cytogenetic analysis of the bone marrow revealed a trisomy 21. The patient received transfusions of packed red cells, and his condition remained stable for the next 7 months. He was then admitted with a chest infection and was treated with broad-spectrum antibiotics with satisfactory response. During his hospitalization there was a gradual increase in his complete blood count values, which persisted, resulting in a normal peripheral blood after 3 months. A bone marrow aspirate performed at that time revealed normal findings with no karyotypic abnormalities, indicating a spontaneous remission. The patient remained stable for the next 6 months; then he recurred with 20% blasts in his bone marrow and reappearance of trisomy 21 in 42% of the metaphases examined. Several hematologic malignancies with spontaneous remissions have been described to date, but they have generally been short and recurrence is the rule, as in the case described. The role of endogenous cytokines in triggering these spontaneous remissions is under question, as the exact mechanism is unknown.