This chapter discusses consumer buyer behavior and the factors that influence it. It presents a model of consumer behavior that shows how marketing stimuli interacts with other stimuli to influence consumer behavior. It identifies four major factors - cultural, social, personal and psychological characteristics - that affect consumer behavior. It also describes the different types of buying decision behaviors and the five stages of the buyer decision process for new and existing products: need recognition, information search, evaluation of alternatives, purchase decision, and post-purchase behavior. Finally, it discusses differences in consumer behavior across international borders.