ABSTRACTThe occurrence of a transitory bone marrow aplasia followed shortly thereafter by acute leukemia is a rare clinical occurrence in children. We report 13 observations involving children between 6 months and 10 years of age. Splenomegaly was observed in five patients and hepatomegaly in two. There was a tricytopenia in five cases, bicytopenia in four, and an isolated cytopenia in the remaining four cases. The phase of marrow aplasia was short, lasting from 6 to 30 days. Complete bone marrow recovery occurred. Remission was spontaneous or followed transfusion or corticosteroid therapy and lasted for 2‐6 months. The leukemia had no particular character when it appeared: There was one case of acute myeloblastic leukemia, 11 cases of acute lymphoblastic leukemia, and one sarcoma. Median survival time was 5‐32 months and there were no relapses of marrow aplasia. In these cases, it cannot be determined whether there is an initially nonleukemia marrow aplasia or if leukemia is present at the onset but undetected, camouflaged, or confined to a few small foci.