Abstract: Objective To explore the clinical characteristics of thyroid dysfunctions (TD) in patients with chronic hepatitis C during interferon combined with ribavirin (RBV) therapy. Methods The clinical data of thyroid dysfunctions in 78 cases of patients with chronic hepatitis C during interferon combined RBV therapy were retrospectively analyzed. There were 58 cases with human recombinant interferon alpha 2 b (IFN-α 2b) therapy and 20 cases with polyethylene glycol interferon alpha 2 a (Peg-IFN-α 2a) therapy in the 78 cases. Results In the 78 cases of patients, there were 17 cases (21.79%) with thyroid dysfunction, then 5 cases with thyrotoxicosis, and 12 cases with hypothyroidism. Sex, the baseline load of HCV RNA, the duration of HCV infection, the time of virological response and the total course of treatment was no significant correlation with the occurrence of TD. Yet age and previous history of TD was significantly correlated with TD. There were 15 cases of patients with transient TD, only 2 cases had to terminate the treatment of interferon. The incidence of TD in Peg INF α-2a group and INF-α 2b group was 10% (2/20) and 25.80% (15/58), respectively. Age (χ2 = 4.974, P = 0.026, OR = 1.073), a history of previous TD (χ2 = 5.123, P = 0.024, OR = 16.569) showed a positive correlation with the incidence of thyroid dysfunction. TD occured mainly in 31-60 days after interferon therapy. Conclusions TD is the more common adverse reactions in chronic hepatitis C with interferon combined with RBV therapy, especially those with previous history of TD. Most of TD is a temporary anomaly, so antiviral treatment should be done under close surveillance.