A statistical decision theory of simple RT is outlined. The theory is based on the view that simple reactions are prepared responses elicited by the triggering of a response release mechanism which can be pre‐set byS, and treatsS's setting of this mechanism as a statistical decision process. The theory is applied with some success to findings concerning the stimulus intensity‐RT relationship, motor and sensory preparation, the distribution of RTs, the effect of forewarning signals, the Donders' a‐and c‐type reactions and so‐called psychological refractoriness. It is suggested that the theory may provide a basis for a more adequate conceptual treatment of