Electrical signals from the brain can be employed to create a direct information channel between the human brain and the computer. Recognizing patterns of these signals can let people’s intentions be expressed with no need of movements. Tracking the user’s gaze on a computer screen is another hands-free method for human-machine interaction. In this thesis, both technologies are combined to develop a hybrid spelling system for people affected by severe disabilities. The Brain Computer Interface system exploits auditory evoked potentials to select letters in order to write words. The Eye Tracking is combined with this system to let the user delete an unwanted letter or to save a word.