Designing and evaluating user interfaces is a complex task. The current focus on user experience (UX) demands user-centered processes that take considerable time and resources, and thus collide with the fast-paced agile methodologies that currently dominate the industry. In this context, academia and industry have proposed the automation of different tasks in the design and evaluation user interfaces (UIs) like prototyping and user testing. Artificial intelligence (AI) techniques such as machine learning have been a considerable help to achieve this. The articles featured in this special issue describe original proposals in the use of AI for UI and user behavior evaluation.