The present study was an attempt to resolve some of the inconsistencies and discrepancies in previous studies examining the relationship between Rotter's locus control construct and voluntary heart rate (HR) change. Twelve internals and 12 externals received two sessions (one week apart) of bidirectional HR control trials with or without feedback. Internals, relative to externals, were better able to increase their HR and showed more improved performance with feedback. Neither group was able to lower their HR significantly during any decrease phase of either session. It was suggested that (a) HR slowing may involve different psychophysiological processes than HR speeding, and/or (b) HR slowing may have been perceived to be a task involving chance rather than skill, in which case no difference between groups would be expected in light of the locus of control literature.