The present analog study compared the effectiveness of an acceptance- and control-based intervention on pain tolerance using a cold pressor task, and is a partial replication and extension of the Hayes, Bissett et al. (Hayes, S. C., Bissett, R.T., Korn, Z., Zettle, R. D., Rosenfarb, I. S., Cooper, L. D., & Grundt, A. M. (1999). "The impact of acceptance versus control rationales on pain tolerance." "The Psychological Record, 49", 33-47) study. Our aim was to test the effects of a nonspecific source of therapeutic change within the context of ACT therapy. Otherwise healthy undergraduates (N = 20) were exposed to a cold pressor task before, immediately after, and 10 min following one of the two interventions. Half of the participants also were assigned to a high demand characteristic condition in which the experimenter maintained close physical proximity, eye contact, and placed subtle social pressure on participants to please the experimenter. The results showed that the most important factor influencing latency to withstand the cold pressor task was social pressure. The acceptance-based intervention was more subject to demand than the control strategy. Evaluative ratings of pain were unaffected by the demand manipulation. The current data suggest that demand characteristics can exert a significant positive impact on the outcome of therapeutic protocols. The implications of this view for acceptance- and control-based psychosocial interventions are discussed. (Contains 3 tables.)