This study describes the synthesis and some pharmacological properties of three new analogs of arginine vasopressin (AVP) substituted in position 3 with (R)-alpha-hydroxymethylphenylalanine ([R]-HmPhe). All new peptides were tested for vasopressor and antidiuretic as well as uterotonic activity. None of the 3 analogs showed any pressor activity and their uterotonic activity was negligible. Only analog [Mpa1,(R)-HmPhe3]AVP exhibited significant antidiuretic activity.