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This paper reviews the design and material evolution of poppet valves used in reciprocating internal combustion engines in the United States. Driving forces which led to the current state-of-the-art technology, such as needs for improved durability and cost effectiveness, are described. This paper also endeavors to predict how valve materials, design, and construction will change over the next two decades in response to continual engine performance improvement demands in a worldwide competitive environment. As a basis for understanding the past evolution and future trends in valve design, the key operating parameters that affect valve function are detailed.