The Workshop on the Future of Antennas was the second of three workshops conducted by the National Research Council's Committee for Science and Technology Challenges to U.S. National Security Interests. The objectives of the workshop were to review trends in advanced antenna research and design, review trends in commercials and military use of advanced antennas that enable improved communication, data transfer, soldier health monitoring, and other overt and covert methods of standoff data collection. The first day's sessions, consisting of five presentations and discussions on antennas and wireless communications and control, were open to committee members, staff, guests, and members of the public. The second day was a data-gathering session addressing vulnerabilities, indicators, and observables; presentations and discussions during this session included classified material and were not open to the public. The committee's role was limited to planning and convening the workshop. This report is organized by topic in the order of presentation and discussion at the workshop. For Day 1 the topics were Future of Antennas, Commercial State of the Art of Wireless Communications and Control, Military State of the Art of Wireless Communications and Control, and Future Trends in Antenna Design and Wireless Communications and Control. For Day 2 the topics were Vulnerabilities of Ubiquitous Antennas, and Indicators and Observables, followed by a wrap-up discussion. Summary of a Workshop on the Future of Antennas describes what happened at the workshop.