As cellular mobile communications increases rapidly throughout the world and interest in ever higher data rates grows, there has been growing demand for additional spectrum for such services. The original spectrum below 1 GHz has been supplemented with additional spectrum up to 3 GHz and now millimeter-wave spectrum above 24 GHz is being added. There now a discussion going on in many countries and in International Telecommunication Union (ITU) circles on repurposing spectrum in the 3.7-24 GHz range. The spectrum of greatest immediate interest and probably of most controversy is the 3.7-4.2 GHz band. This column reviews the present uses of this band and the controversy and potential associated with using for cellular services. Due to the differing procedures of spectrum policy deliberations in various countries, at this time there more information readily available in public sources about this issue in the consideration of the U.S. spectrum regulator, the Federal Communications Commission (FCC), which is used herein to illustrate the issues. However, similar issues can be expected to be raised in other countries as they consider variants of the same proposed repurposing.