Patients with an acute coronary syndrome (ACS) and comorbid depression have a 2-fold higher risk for recurrent ACS and mortality, worse quality of life, and higher costs of care than nondepressed ACS patients. The strength of these observational findings prompted the American Heart Association (AHA) to advise that routine depression screening for ACS patients and referral for depression diagnosis and treatment as indicated occur. Unfortunately, there are no randomized controlled trials (RCT) to inform this large, potentially expensive screening recommendation. And, screening guidelines/advisories in the absence of RCT evidence have recently been extensively criticized (and withdrawn). This poses a serious dilemma for clinicians, health care systems, and for health care policy leaders. A RCT is urgently needed to provide evidence for these different constituents about the costs and benefits of the AHA depression screen and treat algorithm. Two critical gaps in knowledge must be filled to determine if public health would be improved by the AHA strategy for depression screening in post-ACS patients: 1) Does this strategy improve quality-adjusted life years for patients with a recent ACS? 2) Is the cost of providing depression screening and any type of depression treatment within the acceptable and typical amounts reimbursed for health care services? Our specific aim is to determine the quality-adjusted life year benefits and health care costs of following the AHA's advisory for depression screening and then referral for further diagnosis and treatment in post-ACS patients, if depression is found. To accomplish this aim, we will randomize patients from three different, geographically diverse health maintenance organizations to three different groups: 1) to the AHA depression screen and treat if depression is found algorithm (intervention group) or: 2) to receive no depression screening (strong control group) or: 3) to be screened and a primary care provider notified (minimally enhanced control group). Health-related quality of life, depressive symptoms, and costs will be obtained from all patients, so that the benefits and the costs of these three different depression screening strategies can be compared.