Summary of proposed work: 1) Three biologically active peptides (Ala1)-a-adrenocorticotropin-(1-20 NH2) (I), (D-Ala1)-alpha- adrenocorticotropin-(1-20 NH2) (II), and (C14-Ala1)-alpha- adrenocorticotropin-(1-20 NH2) (III) have been synthesized by the solid- phase method. All of the synthetic peptides exhibited high steroidogenic potency, and peptide II was shown to have prolonged steroidogenic activity in vivo. 2) Four biologically active peptides have been synthesized by the solid-phase method: (2-delta-aminovaleric acid)-adrenocorticotropin-(2-19), (3-omega-aminocaprylic acid)- adrenocroticotropin-(3-19), (3-delta-aminovaleric acid)- adrenocorticotropin-(3-19), and (3-4-delta-aminovaleric acid)- adrenocorticotropin-(3-19). The in vivo steroidogenic activity and the in vitro lipolytic activity of the above peptides relative to that of adrenocorticotropin-(1-19) are reported. 3) The solid-phase synthesis of alpha-melanotropin hydrazide, a new analog of alpha-MSH, is decribed. Cleavage of the partially protected peptide from the solid support was accomplished with hydrazine in dimethylformamide. The protecting groups were removed with sodium in liquid ammonia and the product was purified by chromatography on carboxymethylcellulose to give a highly purified and melanotropically active tridecapeptide.