objectives: to identify the opinion of pediatricians and the recommendations of professional organizations and public health institutions regarding the prescription of fluoride supplements. methods: a questionnaire was sent to pediatric doctors. additional information on fluoride supplements was obtained from seven professional organizations and four public health institutions. results: approximately one in every ten pediatricians reported having prescribed some fluorine supplement. the risk of dental fluorosis, when water is fluoridated, was the main reason given for believing that this should not be done. with regard to professional organizations only two gave appropriate responses. the others did not have a satisfactory opinion regarding reasonable use of fluorine. the response of the public institutions was appropriate, even though the ministry of health has not stated a position on the issue. conclusions: one in every 10 pediatricians reported having prescribed supplements containing fluorine to children living in s？o paulo, a city in which the water is already fluoridated. there is, therefore, a need for the public authorities and dental associations to take on their responsibilities with regard to the use of fluoride supplements.