A series of experiments involving the interaction of perceived exertion, selected psychological states and traits, and metabolic responsivity to bicycle ergometry are reviewed. The findings indicate that normal subjects are capable of consistently identifying differences in work load by means of Borg's psychophysical category scale, and these subjective estimates mirror the actual metabolic cost of the work being performed. The exception to this generalization is the case where the subject is neurotic, anxious or depressed since such individuals appear to have difficulty in their perceptual processing of work intensity. Extroverts tend to underate work intensity at heavier loads, and their stated work preference is higher for prolonged work than it is for introverted subjects. Pre-exercise self reports of somatic perception correlated with perceived exertion across a 30-minute work bout. Various psychological states and traits seem to play a role in the perceptual processing of information relating to muscular work, and both metabolic and perceptual responsivity of exercising subjects has been manipulated by means of hypnotic suggestion. It is concluded that a psychobiologic approach to perceived exertion is the most efficacious.