The preventive, and partly the remineralizing, effect of xylitol was shown in Finland in the Turku Sugar Studies in 1971-73. Since then, several clinical trials in many countries have confirmed these results. In Finland, oral health personnel have recommended daily use of xylitol chewing gum in their dental health education. Moreover, commercial companies have advertised xylitol, emphasizing in particular its caries preventive effects. All Nordic dental associations have given their recommendations for xylitol use. The aim of this study was to describe how this health habit has been adopted by Finnish schoolchildren. The study was part of the comprehensive cross-national survey on Health Behavior in School-aged Children (HBSC Study)--a WHO Collaborative Study. The data were collected using standardized questionnaires to which pupils in grades 5 (11 years), 7 (13 years) and 9 (15 years) responded anonymously in school classrooms during the spring term 1998. The response rate varied between 87% (15-year-old boys) and 94% (11- and 13-year-old girls). Among boys, the percentages of daily users of xylitol chewing gum were 47% (11 years), 46% (13 years), and 44% (15 years), and among girls, 57% (11 years), 65% (13 years), and 69% (15 years), respectively. Use of sugar-sweetened chewing gum was very rare (1%), as also was use of chewing gum with other artificial sweeteners (1%). It may be concluded that since 1991 the use of xylitol chewing gum has further increased in Finland and currently more than a half of all schoolchildren benefit from it.