The present study was designed to determine the effects of response interruption and differential reinforcement of other behavior (DRO) on the reduction of hand-mouthing behavior in a quadriparesic adult male client who functions at the profound level of mental retardation. In order to determine the effectiveness of the treatment package, a withdrawal design was used in which baseline (A) and treatment (B) conditions were alternated in an ABAB sequence. The treatment phase consisted of two lOmin treatment periods per day for four consecutive days. Two treatment/withdrawal rotations were followed by nine follow-up observation periods. A preliminary fading process was started following the follow-up periods, which included removal of the reinforcer. Hand-mouthing was reduced by 80% through the use of response interruption and DRO. Hand-mouthing continued to decrease during the nine follow-up observation periods and formal fading procedure. Implications for the extended use of such nonaversive procedures to decrease hand-mouthing behavior in persons with developmental disabilities are discussed.Hand-mouthing is a form of self-injurious behavior (SIB) characterized by contact of the hand(s) or finger(s) with the lips, tongue, teeth, or oral cavity,