During the past 10-15 years the possible side-effects of dental restorative materials, especially due to amalgam fillings, have caused a lively debate in Sweden. There is an extensive literature on the chemical and biological properties of dental materials but no investigations have dealt with the providers' attitudes. The purpose of this study was to find out the dentists' experiences of and attitudes to patients who state they have problems related to dental restorative materials and compare the dentists' subjective assessments of those side-effects in two neighboring countries, Finland and Sweden. Information was collected by postal questionnaires addressed to dentists chosen at random in Finland (n = 625) and in Sweden (n = 960). The response rate was 73 per cent and 72 per cent respectively. The results showed that 99 per cent of the respondents had patients questioning the safety of dental materials. The number of such patients was estimated to be three times higher in Sweden (124 patients per dentist in 1989) than in Finland (39 patients per dentist). More than 90 per cent of the questions from the patients regarded amalgam fillings. Statistically significant differences were found between the respondents' opinions of amalgam, 81 per cent of the Finnish contrary to 59 per cent of the Swedish respondents considered the risk of side-effects to be low when using this material. About 90 per cent of the respondents considered glass-ionomer, gold and ceramic restorations safe, but only half of them were convinced of the safety of composite. A great majority of the Swedish respondents (79 per cent) claimed that the patients should get their fillings changed without odontologic indications if they insisted on it and paid for the treatment in comparison to 22 per cent of the Finnish respondents (p less than 0.001). In case dental insurance was to pay for this kind of treatment it was accepted by 6 per cent of the Finns and 25 per cent of the Swedes. The attitude to amalgam was in general less favorable among the dentists in Sweden than in Finland.