The authors studied the occurrence of common lifestyle risk factors, namely, nonprudent diet, smoking,physical inactivity, and frequent inebriation by alcohol in a cohort of young adults aged 18, 21, and 24 years (n = 484) as part of the Cardiovascular Risk in Young Finns Study in 1986. Risk habits showed significant clustering; the number of subjects was greater than expected in groups with zero and three to four risk habits and less than expected in the group with only one or two risk habits. Stepwise logistic regression analysis was used to find independent determinants for this clustering from a set of socioeconomic, demographic, and behavioral (type A components) determinants. The logistic model suggested several independent risk factors for risk habit clustenng. These included male sex, aggressiveness, and past unemployment. Paying a lot of attention to health habits, higher education (being a student), good self-perceived health, and a high sense of responsibility seemed to be protective factors against risk habit clustering. The accumulation of risk habits was also associated with an atherogenic lipid and blood pressure profile (clustering of high density hpoprotein cholesterol/total cholesterol ratio, triglycerides, and diastolic blood pressure in their extreme tertiles). These findings show that common risk habits cluster among young adults. Knowledge about the determinants of this clustenng will aid in the planning of future preventive strategies against cardiovascular diseases in young people. Am J Epidemiol 1995;142:36–44.