ACM IUI 2019 (https://iui.acm.org/2019/index.html) is the 24th annual meeting of the intelligent interfaces community and serves as a premier international forum for reporting outstanding research and development on intelligent user interfaces. ACM IUI is where the Human-Computer Interaction (HCI) community meets the Artificial Intelligence (AI) community. Registration is now open, please register and book your hotel room as soon as possible (last year, registration was sold out one month in advance!). This year we decided to offer two registration options. Main conference+workshop: Main conference+workshop registration includes the main conference from March 16 to March 20, 2019, with keynotes, paper presentations, posters, demos, workshops, a reception, and a banquet. Workshop only: Workshops will be on March 20, 2019. Registration dates: - Early registration (until Feb 8th) - Late registration (until March 15) - Onsite (after March 15) Please visit https://iui.acm.org/2019/registration.html for more details. Also information on accommodation can be found at: https://iui.acm.org/2019/accomodation.html