Effective navigation is becoming more and more critical to the success of electronic commerce (E-commerce). It remains a challenge for educational technologists and Web designers to develop Web systems that can help customers find products or services without experiencing disorientation problems and cognitive overload. Many E-commerce Web sites are beginning to employ a pull-down menu because it provides the most versatile navigation mechanism. Although the pull-down menu design has been used in other computer applications, it is relatively new on the Web. This study analyzed the navigation effect of the pull-down menu design with three hierarchical information structures (constant, increasing, and decreasing types). The navigation effect was measured by two information searching strategies (searching and browsing) and three users' attitudinal measures (appeal, perceived usability, and perceived disorientation). Three Cyber-shopping malls were developed with the pull-down menu design as well as three information structures. Participants were 58 undergraduate and graduate students at a Midwestern university. Findings provide useful information for designing a pull-down menu and information structure for effective navigation. Results show that there exist better combinations of pull-down menu design and information structure in terms of the efficacy of browsing, the overall appeal of the site, the perceived usability and the users' perceived disorientation. Overall results show that decreasing information structure produced more effective browsing speed, appeal, perceived usability, and disorientation than when information structure was increased. (Contains 33 references.) (Author/AEF)