While manipulating the touchpad, a user’s hand position must be away from the keyboard’s home position. This effect hinders smooth switching between text entry and pointer manipulation, and is considered to be the one of the major drawback of the touchpad against to the trackpoint. This paper introduces ThumbSense, a new input technique aims to solve this problem by automatically sensing users’ input mode based on finger contact to the touchpad. A key on the keyboard, such as the £ ¢ ¡F key, transparently acts both as a normal key as well as a mouse button. This technique is implemented by using the sensor feature of the touchpad, and is possible to apply most of currently available portable computers without requiring any additional hardware/sensors. Keywords Touchpad, touch-sensitive user interfaces, mode sensing.