Wireless distribution services using K/Ka bands have started in Japan for subscriber lines, paving the way to the use of millimeter-wave spectrum for broadband communications. Last year also saw the establishment of consecutive technical standards for 60-GHz indoor, wireless communications systems, thus accelerating possible deployment of these systems. Meanwhile, ongoing national projects such as the Stratospheric Wireless Platform Program are expected to influence the current terrestrial wireless systems as a whole in the near future. This paper reports on the trends in millimeter-wave communication systems along with the key technologies that are essential for them to be created. Emphasis is placed on antenna-circuit integration and high-speed devices from a viewpoint of improving system performance.