This report describes the activities of the Northern New England Cardiovascular Disease Study Group. The group consists of representatives from six institutions: Eastern Maine Medical Center in Bangor, and Maine Medical Center in Portland, ME; Optima Health Care in Manchester and Dartmouth-Hitchcock Medical Center in Lebanon, NH; Fletcher Allen Health Care in Burlington, VT; and Beth Israel-Deaconess Medical Center in Boston, MA. The Northern New England Cardiovascular Disease Study Group maintains a voluntary primary cardiac surgical database that has risk-stratified information on more than 60,000 consecutive patients who have undergone open heart surgical procedures in northern New England since 1987. In 1991, the group reported that significant variation in mortality rate existed between centers, a difference not explained by case mix. The finding led to a regional retrospective review of deaths in an effort to identify "mode of death." Mode of death is defined as that event that started the chain of events ultimately leading to the death of the patient. The most common mode of death was found to be low cardiac output syndrome. This information has led to a regional effort toward prevention, early recognition, and successful treatment of low cardiac output syndrome in the perioperative period.