The effects of 2 personality traits, extraversion and neuroticism, on experimental and clinical pain were characterized in a group of myofascial pain dysfunction (MPD) patients. Extraverts did not differ from introverts in visual analogue scale (VAS) sensory or VAS affective ratings of graded 5-sec nociceptive temperature stimuli (43-51 degrees C) nor in VAS sensory-VAS affective relationships related to their clinical pain. However, high extravert patients scored lower on affective inhibition (Pilowsky Illness Behavior Questionnaire; IBQ) compared to low extravert patients. This result is consistent with previous suggestions that extraverts inhibit overt expressions of suffering less than do introverts. High neurotic patients did not differ from low neurotic patients in their VAS sensory ratings of either experimental or clinical pain. Their VAS affective ratings of both types of pain were marginally higher as compared to low neurotic patients. As hypothesized, high neurotic score patients gave higher VAS ratings of emotions related to suffering and scored higher on items related to affective disturbance on the IBQ as compared to low neurotic score patients. Overall, the results indicate that the personality traits of neither extraversion nor neuroticism affect sensory mechanisms of nociceptive processing but appear to exert their influence by means of cognitive processes related to the ways in which people constitute the meanings and implications of pain.