STUDY OBJECTIVE--The aim was to establish the public's perception of the relative importance of various environmental risk factors for cancer. DESIGN--A postal survey was undertaken using a questionnaire to assess the public's knowledge of cancer morbidity and mortality and the role of lifestyle and genetic risk factors. Sociodemographic data were also collected. SETTING--The survey was completed in the state of South Australia. PARTICIPANTS--A random sample of 1500 names were selected from the electoral rolls of the state. These rolls contain the names of all Australian citizens over the age of 18 years. A response rate of 73% was achieved. MEASUREMENTS AND MAIN RESULTS--The results of the survey showed that the knowledge base of the community was generally high, with few differences across sociodemographic groups. The relative importance of cancer as a contributor to mortality was, however, overestimated and the potential for "cure" underestimated. The role of both diet and cigarette smoking in cancer promotion was widely recognised but there was an overemphasis on the importance of pollution of the food supply compared to imbalance of nutrients. Respondents were more able to assign risk in relation to diet using a food based assessment, compared to a nutrient approach. There was wide acceptability that lifestyle change could have a profound effect on the cancer profile of the community. CONCLUSIONS--With the relatively high degree of awareness and acceptance of lifestyle factors as cancer risk determinants, campaigns which involve skill transfer and removal of barriers to change would appear to be the most relevant approach to improvement in community behaviour.