The plan, testing procedures, and results of an 18 month NIOSH sponsored program to develop improved protective helmets for underground coal miners (SIC-1211) are reviewed. The historical background and objectives of the program are summarized. The design requirements and production specifications for a prototype helmet are discussed, and mining accident data are reviewed to determine the impact, crushing, and penetration potential of various underground injuries. Requirements for helmet compatability with other protective equipment worn by the miner, such as respirators, communications equipment, and noise protective equipment, and for helmet suitability for the tasks and environment of mining, are outlined. The various factors of helmet design studied in tests of existing helmets, which included crush resistance, load distribution, energy absorption, and fit and retention, are described. Design modifications necessitated by helmet test results are illustrated. The authors conclude that the prototype helmet offers underground miners improved impact and crushing protection and is compatible with the equipment, tasks, and environment of the miner.