Abstract: Objective To explore caries prevention effect of pit and fissure sealant for the first permanent molars among school-age children in Guangzhou municipality.Methods With random sampling,examinations on sealant retention and caries were carried out among 5 576 and 4 875 pupils receiving pit and fissure sealant for their first permanent molars two or three years ago at their second year of primary school.School and grade group-matched pupils with the indication of not receiving pit and fissure sealant for the first permanent molars were recruited and examined as two control groups.Results Among the pupils having the pit and fissure sealant 2 years ago,the sealant retention rate was 75.4% and the detection rate of caries was 5.67%,which was 55.55% lower than that (11.48%) among the control pupils; among the pupils having the sealant 3 years ago,the sealant retention rate was 72.2% and the detection rate of caries was 7.04%,which was 40.46% lower than that (11.82%)of the control group.The dental caries rate decreased by 59.39% and 45.11% among the rural pupils receiving the sealant 2 and 3 years ago,which were higher than those among the urban pupils (48.27% and 38.36%).Conclusion Pit and fissure sealant for the first permanent molars is an effective and appropriate measure for the prevention of dental caries among school-age children,especially among children in rural areas.