The purpose of this chapter is to examine the information-processing mech anisms behind elicitation of the orienting response (OR). In the first section, I review theoretical positions of relevance to this issue. On the basis of this review, and a comparison between the various theoretical options, a set of empirical issues are delineated. In the second section, these issues are exam ined in light of a series of empirical studies aimed at analysing preattentive mechanisms behind OR elicitation. In the third and final section of the chapter, the results from these studies are related to the theoretical positions, which are critically scrutinized in the light of the findings.