Millimeter-wave communication uses a frequency of at least 30GHz, which is higher than that commonly used for wireless local-area networks (LANs) and cellular phones. Millimeter waves have been used for business communications and radar in luxury cars; however, their use has not yet spread to the general public. In recent years, an increasing amount of research results on millimeter-wave complementary metal-oxide semiconductor (CMOS) integrated circuits has been reported in line with the increasing attention focused on millimeter waves used for high-speed wireless communication, which can realize a communication speed higher than 1Gbps. We discuss the social background behind this recent change in communication technologies and examine the challenges and future prospects of millimeter-wave CMOS integrated circuits.