Cardiovascular disease accounts for 43 percent of all deaths in the United States. Hypertension affects as many as 50 million Americans, however the causes of essential hypertension are not well known. A new CVD risk factor ("job strain") has emerged as a potential major cause of essential hypertension. By 1995, over 20 studies had found significant positive relationships between "job strain" and CVD, coronary heart disease, all-cause mortality or hypertension. "Job strain" is defined as high psychological workload demands combined with low"decision latitude". An expanded concept of "job strain" which included low workplace social support ("iso-strain") was developed and examined in the study.