Consumers who use interactive Web applications called product comparison agents (PCAs) may be overwhelmed by information and decisions to make, leading to an inability to choose or dissatisfaction with the ultimate choice, a state of "choice overload." Two experiments were designed to test the choice overload hypothesis. Eight choice tasks of different size were presented to subjects. By observing the decision quality, decision time, and decision confidence, we confirmed our hypothesis that choice overload exists when the decision-making task exceeds 24 choices and 5 attributes. Subjects were given different decision-making tools (sorting and short-listing) and conditions (refreshing of information) to deal with the same choice task within the choice-overload range obtained from initial experiment. The use of PCAs required more decision-making effort and resulted in less decision satisfaction than when only one decision-making tool was provided. We believe these findings are relevant to the development of new PCAs, the psychology of decision-making, and the advancement of consumer behavior research.