Voice over asynchronous transfer mode (ATM) is part of an ongoing convergence to a single network technology that supports multimedia services and offers guaranteed quality of service (QoS). This paper explains the economic advantages of such a solution for both carrier networks and enterprise networks compared to traditionally separate circuit-switched networks. We describe how ATM supports voice traffic, as well as the various options defined by the ATM Forum and other standards bodies for voice and telephony over ATM (VTOA). We examine applications of VTOA in both carrier and enterprise network environments, and we describe the various products that form Lucent Technologies' VTOA solutions for the near term and beyond.