Unlike childhood leukemia diagnosed at later ages, where there is an excess risk in males, there is a notable female predominance in infant leukemia. Since abnormalities involving the MLL gene are frequent in infants with leukemia, we asked whether there are gender differences with respect to MLL gene status. Data were combined from seven published molecular studies that examined MLL abnormalities in infants with leukemia. Of 239 cases with conclusive information, there was a female predominance in cases with an MLL abnormality (female:male ratio 1.3); this was in marked contrast to cases with normal germline MLL (female:male ratio, 0.7). These potential gender-dependent MLL frequencies should be explored in large populations of infant leukemia and, if confirmed, future investigations could be directed toward potential etiologic mechanisms.