Abstract: A method is disclosed for enhancing growth of a mammal by administration of a combination of effective amounts of IGF-I and GH so as to enhance the growth of the mammal over the enhancement in growth achieved using either IGF-I or GH alone in an amount equal to that used for either IGF-I or GH, respectively, in the combination. Preferably, the mammal is a child, the IGF-I is native-sequence, mature human IGF-I or human brain IGF-I, and the GH is native-sequence, mature human GH with or without a terminal methionine. In another preferred embodiment, the mammal is a non-human animal of economic importance such as a cow or pig.