Thyrotropin-releasing hormone (TRH) analogues which show relative selectivity for action in the central nervous system have been recognized. Practical syntheses for three of these TRH analogues which show the greatest selectivity,< Aad-His-Tzl-NHz (5),< Glu-His-Pip- OMe (Z), and< Aad-His-Pro-NHz (61, are described. The T it two were prepared by solution methods of peptide synthesis. Compound 6 was prepared by the solid-phase method. ...