The applicability of state-of-the-art repeaters to wireless communication in U.S. coal mines is investigated. Requirements, environment, and system design factors are described. Present f1/f1 and f1/f2 repeater technology and equipment in the mf to UHF bands are reviewed, and system designs based on these are formulated and compared for use in coal mines. F1/f2-type radio repeater systems are presently the most practical for U.S. mine applications. F1/f2 equipment is commercially available in the HF, VHF, and UHF bands, but not below 25 mhz. Although no off-the-shelf repeater equipment presently meets all mine environmental, safety, and user requirements, available UHF (450 mhz) equipment suitably modified, presently offers the most promise for providing wireless communication coverage compatible with the needs of both working sections and haulages. Repeater systems using radiating coaxial cables offer a practical alternative for radio coverage along haulageways. Recommendations are made for the installation, test, and evaluation of a prototype system using modified, commercially available UHF equipment in an operating mine.