Abstract: Objective To exploit the hospitalization rate and its associated factors of hyperthyroidism in urban residents.Methods Hyperthyroidism records were collected retrospectively among urban Changzhou citizens between 1991 to 2004.Data was analyzed using descriptive statistical method.Iodine level of salt was surveyed during 1995 to 2004 in the method of direct titration of standard Na₂S₂O₃ solution.Results Hospitalization of hyperthyroidism(HH)in the area was in a low level of 1.46 per million in 1993.After the universal salt iodization(USI),HH incr eased to a peak of 27.74 per million in 1999,and then droped to 8.83 permillion in 2004.Adjusted by other factors,RR of female against male is 3.175(95%CI:2.907-3.460),RR of the age≥40 against<40 is 2.321(95%CI:2.152-2.503),and RR after USI against before USI is 4.658 (95%CI:4.116-5.270).Conclusion Hospitalization of hy perthyroidism is probably related to USI,and hyperthy roidism induced by iodine should be more closely monitored.