There are provided a novel series of peptide analogs of hGH-RH(1-29)NH2 and hGH-RH(1-30)NH2 which show high activities in stimulating the release of pituitary GH in animals. They retain their physiological activity in solution for extended periods of time and resist enzymic degradation in the body. These novel and useful properties appear to be due to novel substitution patterns ant at the 1, 15, 27 and 29 positions on the peptide.