Objective:To investigate the prevalence of thyroid dysfunction in Nanjing community population. Methods:The residents who had lived in Nanjing for at least five years and were more than 20 years old were selected by a stratified cluster sampling technique. 1 266 subjects were selected for questionnaire,physical examination and serum thyroid function test. Results:① Prevalences of overt hyperthyroidism,subclinical hyperthyroidism,overt hypothyroidism and subclinical hypothyroidism were 0.55%,1.74%,0.32% and 4.82% respectively in Nanjing city. ②The prevalences of overt hyperthyroidism,subclinical hyperthyroidism,overt hypothyroidism and subclinical hypothyroidism in females there all higher than those in male,however,the difference was not significant. ③ The prevalence of hypothyroidism increased significantly with age(ρ=0.0971,P=0.0005). Conclusion:Thyroid dysfunction,especially subclinical thyroid dysfunction is common in Nanjing. Screening,evaluation and intervention for thyroid dysfunction is necessary.