As the number of functions in a menu increases, users have more difficulties in finding a desired function. Previous studies have shown that some functions are selected more frequently than others, and have suggested adaptive menus that support the selection of frequently used functions. Interestingly, studies on an adaptive toolbar are not easy to find as opposed to many studies on adaptive menus. This study suggested an adaptive toolbar (AT) that supported function selection, and conducted a usability test. Five or ten functions were presented in the AT according to the frequency of use or recency of use. A total of sixteen males in their twenties participated in the test. They freely selected functions from the menu or from the AT, and their pattern of selecting functions was analyzed. The results showed that the AT was more frequently used than the menu as time passed. The AT based on the recency of use showed more effective performance than that based on the frequency of use. In addition, keeping ten functions was better than five functions in terms of both performance and preference.