Abstract: Objective The present study was designed to investigate the prevalence of caries among senior high school students in the city of Hangzhou and provide a scientific basis for the prevention of caries.Methods A total of 28 730 students(male 12 922 and female 15 808)from 15 senior high schools(9 occupational and 6 ordinary high schools)were enrolled by random cluster sampling for the health examination program of Hangzhou from 2003 to 2005.The oral cavities of the subjects were examined and documented by dental professionals according to Executive Protocol of Research on Students' Health Condition in China,2000.The prevalence of caries among senior high school students was evaluated by the rank sum test and correspondence analysis.Results The prevalence of caries was different in different age groups in different years with a higher incidence of the condition among the age groups of over 18 years,18 years and under 16 years in 2003,2004 and 2005,respectively. Conclusion The prevention and care of caries for younger senior-high-school students are to be substantially reinforced.