The four papers in this special section explore applications, systems, methodologies, and technologies that relate broad aspects to realize successful conversational user interfaces and interactions. Speech recognition has become a part of our daily lives. Today, we can enjoy a wide array of conversational user interfaces and speech-based interactive services, from speech-based personal assistants in our smartphones and smart speakers, e.g.,Amazon Echo, Alexa, Cortana, and Google Home, to chatbots in traditional messaging interfaces. These interfaces are becoming pervasive as reflected by the exponential growth in their adoption. Hence, the expectations are that computer based conversational systems will soon reach the level of human–human conversation.