Earlier studies demonstrated that psychoneurotic patients aroused and confused by ether inhalation showed significantly greater responses to persuasive communications than patients in a state of low arousal.The present study explored: a) the effect of arousal without confusion on patients' suggestibility; and b) the role of attribution of the source of arousal on the acceptance of the communication. Forty-two patients were divided into three groups. An adrenalin inhalant served as the arousing substance. Two groups received as part of their therapy three adrenalin arousal sessions during which a persuasive communication was given. One group was informed,i.e., knew that they were receiving an arousing inhalant; the second group did not know that the inhalant was arousing; the third group served as a control group and received a pharmacologically inert inhalant.Short term attitude change, measured on Osgood's semantic differential, was identical in the informed and uninformed adrenalin group. Thus, not knowing the source of arousal did not heighten patient's readiness to accept an apparently clarifying explanation and therefore did not increase his suggestibility. However, the combined adrenalin groups showed a regular response pattern to the intervention significantly more frequently than the control group. They also showed significantly more directional attitude change in the second experimental session than the control group. Although one has to conclude that adrenalin arousal had some effect on patients' suggestibility, the ratings of therapist performance and patient response suggest rather complex interactions. At the end of the study the adrenalin patients, but not the control group, exhibited increased cardiac lability to focal topics which had been discussed under adrenalin arousal in previous sessions. This finding suggests that some form of association may have occurred between the focal topic and the emotional response.