The project originated in the Epidemiology and Biometry Program of the Division of Epidemiology and Clinical Applications. The concept derived from an NHLBI Task Force on Research in Epidemiology and Prevention convened in 1993, in which investigation of subclinical disease and its progression to clinical disease was recommended as a major focus of future NHLBI population studies. This was followed by a Special Emphasis Panel on Longitudinal Cohort Studies in June 1995, which strongly recommended studies based on subclinical disease measures, and the inclusion of underrepresented minorities, particularly Hispanics, in population based research. A subsequent Special Emphasis Panel on Use of Cardiac EBCT and MRI in Epidemiologic Studies of Cardiovascular Disease in June 1996, recommended inclusion of carotid and cardiac MRI and EBCT in elucidating the progression of subclinical to clinical disease and identifying subclinical disease characteristics most strongly associated with increased risk. In November 1997, the Requests for Proposals were released for the Coordinating Center, Field Centers, Special Laboratory Center, Ultrasonography Reading Center, Magnetic Resonance Imaging Reading Center, and Electron Beam Computed Tomography Reading Center.