Several investigations have evaluated the degree of discomfort that patients experience during orthodontic treatment, but most of the research centered on tactile sensory (touch) threshold, reaction to spacers used to separate the teeth or reaction to the initial leveling wires, and the periodic adjustment of the appliances. The purpose of this investigation is to determine the discomfort threshold for patients undergoing orthodontic treatment at the time immediately before appliance removal. Such information will be useful in determining the force levels that patients can tolerate during debonding. From the findings in this study the following can be concluded: (1) The threshold of patient discomfort, at the time of debonding, is significantly influenced by two factors: the mobility of the tooth and the direction of force application. Sex and tooth type differences also influence the discomfort threshold but to a lesser degree. (2) At the time of debonding, patients can withstand intrusive forces significantly more than forces applied in a mesial, distal, facial, lingual, or an extrusive direction. The clinical implications of these findings are discussed.