The problem of this study was to analyze the effects of contingent reinforcement on the presence of thoughts defined as anxiety responses. The two types of data, observed and introceptive, were used to determine the effects of reinforcement. The observed data from the peripheral physiological pre- and post-measures included heart rate, blood pressure, and the Taylor Manifest Anxiety Scale data. The introceptive data supplied by subjects were the daily percentages of anxious thought detections subsequent to a baseline period. The daily percentages were formed by the subject's monitoring his own thoughts, with the monitoring prompted by an automatic tone device which emitted a tone approximately every four minutes. The daily percentage of anxious thoughts was formed by dividing the number of tones the subject heard into the number of anxious thoughts occurring at the time of the tone.The problem of this study was to analyze the effects of contingent reinforcement on the presence of thoughts defined as anxiety responses. The two types of data, observed and introceptive, were used to determine the effects of reinforcement. The observed data from the peripheral physiological pre- and post-measures included heart rate, blood pressure, and the Taylor Manifest Anxiety Scale data. The introceptive data supplied by subjects were the daily percentages of anxious thought detections subsequent to a baseline period. The daily percentages were formed by the subject's monitoring his own thoughts, with the monitoring prompted by an automatic tone device which emitted a tone approximately every four minutes. The daily percentage of anxious thoughts was formed by dividing the number of tones the subject heard into the number of anxious thoughts occurring at the time of the tone. The main findings in this study were 1. Although not statistically significant, the experimental subjects were found to demonstrate consistently lower mean heart rate and blood pressure following the experimental period. The control subjects' scores were nonsignificantly greater for heart rate and blood pressure at the conclusion of the study. 2. The results further suggested that contingent reinforcement alone did not produce the significant shifts found in the thought frequency of individual subjects. It is likely that both reinforcement and thought monitoring had