Today chat-bot or conversational-agent platforms are ubiquitous. Major technology companies, including Amazon, Google, Apple, Facebook, Microsoft, IBM, as well as multiple start-ups are providing them. But current UX design methodologies and guidelines, intended for graphical interfaces, such as web and mobile, do not apply. In conversational interfaces, the user experience is primarily in the sequences of turns of chat or voice. Although the field of Natural Language Processing (NLP) provides powerful tools for analyzing bits of language, it does not provide guidance on how to string bits of language together into sequences that approximate those of natural human conversation. From the demand for applications on these platforms, a new role is emerging: the conversational UX designer. Currently, the work of conversational UX design is falling on developers, visually oriented interface designers or subject matter experts, none of whom possess the required skills for such work. Instead, what is needed is a person with both experience in UX design and a formal understanding of human conversation (social science). This book provides this new type of UX designer with a collection of studies by HCI researchers and industry practitioners that focuses on key issues in designing conversational user experiences. Each team of authors presents conversational systems and/or user studies and reflects on challenges that are unique to designing conversational interfaces. In addition, the book introduces UX designers to Conversation Analysis (CA), a field within sociology, that provides a treasure trove of empirical models of how people naturally talk and thus a scientific foundation for the creation of conversational UX patterns. General design themes in the book include: the structure of human conversation, agent knowledge, agent misunderstanding and agent design.