Menu-driven interfaces are frequently employed for user interfaces on many electronic products. Due to space constraint, a single or multi-line display is popularly used to show menu items unlike the software interfaces. Single or multi-line display present 8 .approx. 21. characters on an LCD screen and the user selects items using a series of button pushes. Multi-line displays are different from the single-line ones in the following aspects. First, they can present multiple line of information at the same time. Second, they can present menu items in a various way compared to single-line ones. However, due to their space constraint multi-line displays have many limitations compared to ordinary displays which usually use 14" screens. Therefore, guidelines are necessary for designing efficent multi-line display menus interfaces. In this study, a human factors experiment was conducted to examine the effects of three design variables which might affect the usability of a multi-line display menus. Factors investigated include menu structure, number of lines on the display, and item presentation method. Usability of the multi-line display menus was measured quantitatively in terms of four different aspects: speed, accuracy, inefficiency and preference. The analysis of variance was used not only to analyze the main effects of the factors and their interactions but also to see the differences between the single-line display menus and multi-line display ones. A set of design guidelines drawn from this study can be applied to the design of the user interfaces of a various types of electronic consumer products.