It appears that serum-cholesterol level may serve as an important mediator between psychological variables and coronary heart disease (CHD). From a review of the literature it is concluded that (1) psychological stressors significantly elevate serum-cholesterol level and (2) psychological characteristics like the Type A-pattern and depression are positively correlated with serum-cholesterol levels. This suggests that the relationship between CHD and stress and coronary prone behavior may be partially explained by the mediating role of serum-cholesterol. A more careful consideration of psychological variables may be helpful in reducing the substantial amount of unexplained variance in cholesterol levels.