The microstructures of materials produced by plasma spraying or detonation gun techniques consists of thin lenticular particles with a very fine grained (perhaps even amorphous) structure. They are rapidly quenched from the molten, or near molten state, and may have a high degree of residual stress. This review is concerned with the relationship between these unique microstructures and the properties of the material. The areas of bond strength, transient and residual stresses, density, corrosion characteristics, and wear resistance, as well as mechanical, thermal, and electrical properties are at least briefly surveyed. The methods of deposition, i.e., plasma torch operating conditions, heat transfer to the particles, etc., are not covered. It is evident that, although a sufficient amount of information is available for most engineeering applications of these materials, a great deal remains to be learned about the fundamental relationships between their structure and properties.