This is a brief examination of the theoretical and empirical material on the phenomenon of backward conditioning. It is concluded that the effect is a real one but distinct from the process of forward conditioning. Instead of signaling the onset of the unconditioned stimulus, it signals its termination. Thus, the acquired properties of forward and backward conditioned stimuli are opposite, just as are the properties of the onset vs. the termination of any unconditioned stimulus with which they might respectively be associated. 15 references.