The association between Type A behavior and change in coronary risk factors among young adults. The association of Type A/B behavior pattern and changes in blood pressure, total serum cholesterol, serum triglyceride, body mass, and smoking was estimated in a cohort of 375 young Black and White men and women from a rural county in Central Kentucky between 1978-79 and 1985-88. Type A participants experienced significant increases in systolic (2.90 +/- 1.29 mmHg) and diastolic (3.80 +/- 1.17 mmHg) blood pressure and in cigarette smoking (3.26 +/- 0.89 cigarettes per day) over the eight-year follow-up period, but Type B participants experienced no change. Type A and B individuals showed similar changes in total serum cholesterol, serum triglyceride, or body mass. Differences between behavioral types in blood pressure were present for women but not men, and for Blacks but not for Whites. These findings suggest a possible significance of the Type A pattern for the development of cardiovascular risk of young adults. 