The tetradecapeptides of the formula ##STR1## wherein X is H--Ala--D--Ala, H--D--Ala--Gly, or H--D--Val--Gly; and X is Ala--Leu, Ala--Phe, Ala--D--Phe, D--Ala--Phe, or D--Ala--Cha; or the non-toxic, pharmaceutically acceptable acid addition salts thereof; inhibit secretion of growth hormone, while not materially inhibiting the secretion of insulin or glucagon. Intermediates used in the synthesis of the tetradecapeptides are also described.