Twenty subjects were conditioned to raise their operant heart rates during the presentation of one stimulus and to lower operant heart rate during the presentation of a second stimulus. A 2 by 2 factorial design was utilized to examine the effects of proprioceptive awareness [high overall score on the Automonic Perception Questionnaire (APQ) vs. low APQ score] and instructions about the response-reinforcement contingencies (informed subjects vs. uninformed subjects) on operant heart- rate control. The results indicated that informed subjects achieved better control over operant heart rate than uninformed subjects. No effects attributable to APQ score were detected. It is suggested that proprioceptive awareness may influence heart-rate control when no external feedback is available (e.g., Bergman & Johnson, 1971), or when external feedback is relatively weak (e.g., Blanchard, Young, & McLeod, 1972), but information about contingencies of reinforcement appears to have more impact on heart-rate control than proprioceptive awareness when relatively powerful external feedback is available. The heart-rate results appeared to be relatively independent of changes in skin responding and cephalic pulse amplitude.