One opiate hypothesis suggests that self-injurious behavior (SIB) is related to elevated sensory thresholds. The present study examined the relationship between scores on the Motivation Assessment Scale (MAS) (Durand and Crimmins, 1988), a 16-item scale designed to determine variables that maintain SIB in developmentally delayed individuals, and response to naltrexone (an opiate blocker). High baseline levels of SIB in 20 subjects were significantly correlated with observations that SIB was maintained by need for attention as measured by the MAS. There were no significant correlations between scores on the MAS and change in SIB to the most effective dose of naltrexone (2.0 mg/kg). The present findings did not support the relationship between response to naltrexone and sensory scores on the MAS. © 1995 Plenum Publishing Corporation.