Abstract: Recent advances in mobile computing allow the users to deal with 3D interactive graphics on handheld computers. Although the computing resources and screen resolutions grow steadily, user interfaces for handheld computers do not change significantly. Consequently, we designed a new 3-DOF interface adapted to the characteristics of handheld computers. This interface tracks the movement of a target that the user holds behind the screen by analyzing the video stream of the handheld computer camera. The position of the target is directly inferred from the color-codes that are printed on it using an efficient algorithm. The users can easily interact in real-time in a mobile setting. The visualization of the data is good as the target does not occlude the screen and the interaction techniques are not dependent on the orientation of the handheld computer. We used the interface in several test applications for the visualization of large images such as maps, the manipulation of 3D models, and the navigation in 3D scenes. This new interface favors the development of 2D and 3D interactive applications on handheld computers.