Hostility, a broad personality dimension comprised of behavioral tendencies, cognitive biases and emotional or motivational characteristics appears to play an important role in the development of coronary heart disease (CHD). Furthermore, hostility apparently is important, not only as a function of its direct relationship to disease development, by virtue of its well documented link to a wide range of other risk factors, including life style factors (e.g., tobacco and alcohol use, imprudent diet), cardiovascular reactivity to stressful circumstances, and physiological indices (e.g., reactivity to acute stress, lipid levels, platelet activity, glucose regulation). It has been hypothesized that a common pathway underlying each of these factors is described by the serotonin system and by (dys) regulation of central serotonin pathways. Indeed, studies 1 and 2 of this program project application are devoted to an elaboration of this pathway as underlying behavioral, psychological, physiological and metabolic contributors to the development of CHD. The focus of this project is on the impact of short treatment with a selective serotonin reuptake inhibitor (SSRI) on hostility and the wide range of associated risk factors for CHD. Should this study prove successful, it will have the potential of significantly impacting treatment approaches that are aimed at reducing risk for the development and progression of CHD.