One of the fundamental concepts in Marketing is the notion of satisfying the needs and desires of the consumer. In order to find the satisfaction antecedents, the expectations disconfirmation paradigm has been the most popular and robust model among satisfaction researchers. This dissertation empirically tests the antecedents of online consumer satisfaction using the expectancy-disconfirmation paradigm in the e-commerce domain. A laboratory experiment was conducted using a Web site that simulates a bookstore. Using constructs from marketing and information systems research, it was found that usefulness, adequacy, sufficiency and needs fitting are the main factors that determine satisfaction when the Web is used in the process of decision making. The analyses, using structural equation modeling, suggest that expectations affect satisfaction only via the disconfirmation effect, and there is not a direct effect. Expectations act as an adaptation level; there is an assimilation effect that influence satisfaction indirectly through perceived disconfirmation. Performance influences satisfaction through two mechanisms, directly via perceived performance and indirectly via the disconfirmation effect. The model that included performance, disconfirmation, and expectations as direct antecedents of satisfaction found that performance dominated the formation of satisfaction.