Background: Survivors of myocardial infarction (MI) or stroke are at high risk for subsequent cardiovascular events. There is limited assessment of the effectiveness of risk factor modification through current secondary preventive strategies in the US population. We determined the adequacy of risk factor modification in 1252 survivors of MI, stroke, or both in a nationally representative sample of US adults and identified factors related to inadequate control of risk factors. Methods: The adequacy of control for hypertension, diabetes mellitus, cigarette smoking, alcohol use, and hypercholesterolemia was assessed by personal interview, blood pressure measurements, and serum glycosylated hemoglobin and cholesterol levels in 17752 US adults who participated in the Third National Health and Nutrition Examination Survey between 1988 and 1994. We also evaluated the role of potentially related factors, including age, sex, race/ethnicity, educational attainment, socioeconomic status, and medical insurance status using multivariate logistic regression analysis. Results: Of 738 known hypertensive persons, hypertension was uncontrolled in 388 (53%). Previously undiagnosed hypertension was detected in 138 others (11%). Of 289 diabetic persons, serum glucose control was inadequate in 141. Of 1252 survivors, 225 (18%) were currently smoking, and heavy alcohol use was observed in 56 persons. Hypercholesterolemia was poorly controlled in 185 (46%) of 405 persons with known hypercholesterolemia. Undetected hypercholesterolemia was observed in 160 persons (13%). In the multivariate analysis, high-risk profiles were more likely to be observed in persons aged 46 to 65 years, women, and African Americans. Conclusions: High prevalence of inadequate secondary prevention was found in a subset of the US population at highest risk for stroke and MI. Considerable efforts are required to effectively implement risk factor modification strategies after MI or stroke, particularly in middle-aged persons, African Americans, and women.