A pilot study of knowledge and behavior regarding primary cancer prevention was conducted in a tri-ethnic urban community. Knowledge of smoking and dietary risk factors was substantial, but awareness of cancer safeguards involving reduced sun exposure and mouth and proctological examinations was low. One of five respondents had taken measures to prevent cancer, and these persons tended to rate their own risk higher than respondents who made no life-style changes. Self-motivated behavior change focused on avoidance of cancer-promoting food. Blacks differed from whites and Mexican-Americans in awareness of cancer cause and prevention, particularly regarding dietary factors and behavior modification. The findings have implications for the design of cancer control measures in multiethnic communities.