This investigation of the design and performance of high-speed spring loaded cam systems attempts to relate the design technique to a more realistic model of the system. The testing of the validity of experimental and analytical results is also a requirement that has received particular attention. Where appropriate, experimental, analytical and design techniques are examined in a more general way. The starting point of this work is the author's study of pushrod operated valve gear in an automobile engine. Investigations have been continued on a variety of engines, all having the basic common factor of a controlling valve spring. The results are therefore particularly relevant to this class of system and appropriate to the types of motion controls required to operate automobile valves efficiently.