As part of the National Heart and Lung Institute multicenter study of twins, 190 twin pairs (93 MZ, 97 DZ) residing in California and aged 44-55 years were comprehensively studied for all risk factors for coronary heart disease and for Behavior Pattern Type A or B. Psychological tests included MMPI, CPI, 16 Cattell PF, Cough Adjective Check List (ACL), Thurstone Temperament Schedule (TTS). Heritability at statistically significant levels was found only for scales of TTS. Twelve scales of ACL and five scales of TTS showed significant correlations with Behavior Pattern Type A-B as well as with several risk factors, including blood pressure and serum lipids. Multiple regression equations were constructed for those characteristics accounting for significant and unique portions of the total variance of Type A-B Behavior. The use of certain scales of ACL and TTS may provide a new questionnaire for screening purposes in the assessment of Behavior Pattern Type A-B.