A series of compounds has been synthesized and demonstrated to be antagonists of V1 receptors both in vitro and in vivo. These compounds are structurally related to the 1-(4-piperidyl)-2(1H)-quinolinones, including OPC-21268, an orally bioavailable AVP V1 antagonist with high V1 specificity. It has been found that the introduction of an acetamide group on the terminal alkoxy chain of 41-44 leads to an increase in oral activity. Certain of these compounds may have efficacy in the study of AVP V1 receptors.