Abstract: This invention is a mouse for positioning a cursor on the screen of a computer monitor and for inputting computer program instructions. The mouse is conveniently held in the palm of the user's hand. The mouse has a relatively thin and flat body portion, preferably less than about ½″ thick at its widest point, for being received in the palm of the user's hand. The mouse body has buttons for performing normal mouse functions. The mouse also has a head portion which is at least as large as the body portion, for extending out of the palm of the hand of the user. The head portion is adapted to provide a track ball or other cursor positioning switch, as well as a scroll or a click function. All mouse actions, i.e., track ball, buttons and so forth, can be accomplished without removing the user's hand from the keyboard.