This paper develops and tests an instrument to measure online investment self-efficacy, defined as an individual's perceived ability to utilize online technologies to accomplish investing-related tasks. A series of empirical studies were conducted to establish the measure's psychometric properties. The results suggest that the measure exhibits admirable levels of reliability, as well as convergent, discriminant, and nomological validity. As predicted by theory, computer self-efficacy was found to serve as an important precursor to online investment self-efficacy. Furthermore, online investment self-efficacy played a significant role in fueling investor preference for the traditional (full-service) or online investing approach. More efficacious investors tended to prefer Web-based technologies as a vehicle for investing, whereas less efficacious individuals favored the traditional method.