The nature and extent of group differences in pain tolerance according to age, sex and race were examined. The method of pain tolerance determination was mechanical pressure on the Achilles tendon, performed on 4 1 , 119 subjects as part of the Kaiser-Permanente Automated Multiphasic Screening examination. The results showed that, on the average, a) pain tolerance decreases with age; b) men tolerate more pain than women; and c) Whites tolerate more pain than Orientals, while Blacks occupy an intermediate position. When the results of this study are compared with earlier work, it appears that, with increasing age, tolerance to cutaneous pain increases and tolerance to deep pain decreases.Differences in patients' pain tolerance have been a continuing source of interest and concern to their physicians. Some individuals appear to bear severe pain with surprising equanimity, while others react to more moderate pain with apprehension and emotional turmoil.A test of pain tolerance was included in the routine multiphasic health examination of more than 40,000 subjects in the hope that the findings would be clinically useful. While the clinical value has yet to be demonstrated, rather clear-cut differences in pain tolerance according to age, sex and race were noted. These differences may reflect important cultural and biologic variability in pain reaction.