Recent research demonstrates the importance of inflammatory parameters in the etiology and prognosis of the acute coronary syndrome (ACS). This study explored relations between psychological factors and immunological parameters routinely measured among ACS patients. Forty-two ACS patients completed questionnaires assessing perceived-control, emotional support, hostility, and life-events 2-4 days after hospitalization. Data on total leukocytes and percentages (%) of monocytes, %neutrophils, and %lymphocytes upon admission to hospital were collected from computerized medical charts as well as various biomedical information and risk-factors (e.g., diagnosis, left-ventricle-LV functioning, smoking, and hypertension). Of all significant biomedical variables, LV-function and arrival-time correlated uniquely with total leukocytes. Controlling for LV-function and arrival-time, hostility and life-events positively correlated with %monocytes, and perceived-control and emotional-support inversely correlated with %monocytes. Emotional-support was positively correlated and life-events were negatively correlated with %neutrophils. Macrophages play a pivotal role in plaque instability, the trigger of an ACS. This initiating role, and our finding of a relationship between recruitment of monocytes and a poor psychosocial profile, predictive of ACS, are consistent with a PNI component in the pathophysiology of ACS.