The political nature of fluoridation is due in part to public misconceptions about its purpose, and about its efficacy and practicality in preventing tooth decay as compared with other preventive practices. This paper describes a public opinion survey conducted in Portland, Oregon in May 1980, immediately following a referendum that repealed an earlier vote to fluoridate Portland's water supply. A household interview survey was conducted of 313 Portland residents aged 18 and over. The primary objectives of the survey were to: 1) determine attitudes on fluoridation; 2) gauge the effectiveness of several pro- and antifluoridation arguments; 3) determine key target populations for fluoridation education efforts; and 4) determine the relative impact of different sources of information about fluoridation. Among the significant findings of the survey were: 1) preventive practices involving fluorides were rated less important to dental health than other preventive practices; 2) 71% of respondents knew the purpose of fluoridation; 3) newspapers were the predominant source of information about fluoridation; and 4) the "loss of freedom of choice" was by far the most powerful argument against fluoridation.