Objective:To study the influence of lithium carbonate or prednisone administration on the dosage and efficacy of radioiodine treatment (131I) in hyperthyroid patients. Methods: Seventy five patients with primary hyperthyroidism were divided into 3 groups randomly:patients treated only with 131I(control group,n = 25),patients administered lithium carbonate in a daily dose of 0.75 g/d with 131I(lithium carbonate group,n = 25),patients took orally prednisone in an initial dose of 1 mg/kg with 131I (prednisone group,n = 25). Therapeutic doses of 131I and efficacy were observed. Results: Compared with the control group,the therapeutic dosage of 131I was reduced obviously in lithium carbonate group(P < 0.05),but curative effect had not significant improvement(P > 0.05). The therapeutic dosage of 131I for prednisone group was higher than control group,but there was no significant difference between two groups(P > 0.05),while the efficacy was improved significantly (P < 0.05). Conclusion: In patients with hyperthyroidism,lithium carbonate can reduce 131I dosage,but no improvement on the treatment effect;prednisone had no significant effect on dose of 131I therapy,but can increase the efficacy of 131I.