The effects are investigated of locus of control on learning to accelerate and decelerate heart rate over a number of training sessions. 15 subjects who scored internal in locus of control and 15 who scored external were trained to change their heart rates. Subjects were given two training sessions in speeding heart rate and two in slowing heart rate. Results indicated that during the initial training sessions, internals were better able to increase their heart rates than externals; the externals were better able to decrease their rates than internals. However, this association diminished to nonsignificance when additional training sessions were provided. These results argue for routinely conducting a number of training sessions to avoid any premature statement of a relationship between personality measures and learned control of heart rate.