ABSTRACT: In 4 experiments, undergraduate Ss classified visually presented target words as pleasant-unpleasant words or male-female first names. Prime words were similar (congruent) or dissimilar (incongruent) in meaning to targets. Brief duration of prime words (17, 33, or 50 ms), along with pre- and postmasking, prevented most Ss from perceiving their physical and semantic properties. By constraining response latencies to fall within a response window--a narrow time band that occurred earlier than Ss would ordinarily respond--these experiments consistently produced subliminal priming effects, indicated by greater error rates for incongruent than congruent priming trials. This conclusion was confirmed by analyzing magnitude of priming as a regression function of prime perceptibility using the method of A. G. Greenwald, M. R. Klinger, and E. S. Schuh (1995). The data of each experiment passed their significant-intercept criterion for demonstrating unconscious cognition.