Mobile visualization is becoming more prevalent, and new mobile device form factors and hardware capabilities will continually emerge in the coming years. Therefore, it is timely to reflect on what has been discovered to date and to look into the future. This Dagstuhl seminar brought together both established and junior researchers, designers, and practitioners from relevant application and research fields, including visualization, ubiquitous computing, human-computer interaction, and health informatics. Five demos and five tutorials gave participants an opportunity to share their experiences and research, and learn skills relevant to mobile data visualiza-tion. Through brainstorming and discussion in break-out sessions, along with short report back presentations, participants identified challenges and opportunities for future research on mobile data visualization.