Subjects completed a baseline stimulus matching procedure designed to produce two symmetrical stimulus relations; A1–B1 and A2–B2. Using A1, B1, and two novel stimuli, subjects were then trained to produce a common keypress response for two stimuli and a second key-press response for two further stimuli across two blocks of response training. During one block, the reinforcement contingencies were consistent with baseline relations (i.e., A1 and B1 shared a response function), whereas during the other block they were not. Thirteen of 18 subjects who completed the procedure showed a response class acquisition rate differential across the two test blocks in the predicted direction. It is suggested that this procedure may serve as a behavior analytic alternative to popular implicit tests. It provides a nonrelative measure of stimulus association strength and may display superior procedural implicitness over other tests.