A variety of factors contribute to the initiation of translation. Eukaryotic initiation factor 4H (eIF4H) was purified to near homogeneity from rabbit reticulocyte lysate and shown to stimulate translation in an assay deficient in eIF4F and eIF4B (1). eIF4H induces the RNA-dependent ATP hydrolysis catalyzed by the initiation factors eIF4A and eIF4B (1,2). eIF4H was further shown to stimulate the initial rate and extent of eIF4A-mediated mRNA secondary structure unwinding (3).