The effect of CS-UCS interval on acquisition of eyelid conditioning with 120 college students was the same whether onset or termination of light served as CS. In addition to the primary reflex or alpha response to light, an off response (OR) was observed which was analogous to the alpha except that it occurred as a response to light termination. Found alpha conditioning most marked with short CS-UCS intervals, but this trend was not significant with ORs. Conclude that termination of a stimulus is just as critical a feature for conditioning as its onset. 17 refs. (PsycINFO Database Record (c) 2006 APA, all rights reserved)