In this study, the sensory status of 4 nonverbal adults with mental retardation and severe self-injury was examined using skin temperature measures prior to opiate antagonist treatment. Double-blind, placebo-controlled, experimental ABAB designs were used to evaluate the effects of naltrexone hydrochloride (1.5 mg/kg/day). For each participant, the body site targeted most frequently for self-injury was associated with altered skin temperature and reduced by naltrexone. In all cases, neither infrequent self-injury body sites nor non-self-injury body sites were associated with altered skin temperature. Further controlled studies are warranted to examine the value of assessing pain status and skin temperature in nonverbal patients with mental retardation and related developmental disabilities who present with tissue-damaging SIB.