In the last five years, work on software that interacts with people via typed or spoken natural language, called chatbots, intelligent assistants, social bots, virtual companions, non-human players, and so on, increased dramatically. Chatbots burst into prominence in 2016. Then came a wave of research, more development, and some use. The time is right to assess what we have learned from endeavouring to build conversational user interfaces that simulate quasi-human partners engaged in real conversations with real people. This workshop brings together people who developed or studied various conversational agents, to explore themes that include what works (and hasn't) in home, education, healthcare, and work settings, what we have learned from this about people and their activities, and social or ethical possibilities for good or risk.