Book excerpt: This book constitutes the refereed proceedings of the First International Symposium on Handheld and Ubiquitous Computing, HUC'99, held in Karlsruhe, Germany in September 1999. The 23 revised full papers presented together with four invited keynote contributions, 26 reviewed posters, and two panel statements were carefully reviewed and selected from a large number of paper submissions. The papers are organized in topical sections on handheld and wearable appliances, location-based services, smart devices and smart environments, handhelds in distributed systems, handheld and wearable CSCW, context-aware mobile applications, interacting with environment, and interacting with handhelds.