We assessed risk factors for sudden coronary death among persons without a history of coronary heart disease (unexpected sudden coronary death) and persons with a history of coronary heart disease (sudden coronary heart disease death). We analyzed national data to calculate death rates and odds ratios for both types of sudden coronary death. Among modifiable factors that we examined, only cigarette smoking increased risk for unexpected sudden coronary death [odds ratio (OR) = 1.8; 95% confidence interval (CI) = 1.2-2.7]. Diabetes mellitus (OR = 3.8; 95% CI = 2.5-5.8 for women), cigarette smoking (OR = 1.5; 95% CI = 1.0-2.1), and hypertension (OR = 1.4; 95% CI = 1.1-1.9) increased the risk for sudden coronary heart disease death. Etiologic factors for sudden death appear to differ depending on the presence or absence of coronary disease. With preexisting coronary disease, factors associated with chronic coronary disease may elevate sudden death risk; without coronary disease, factors that provoke ventricular arrhythmias may trigger sudden death.