Lithium carbonate was tried in 27 patients with Graves' disease to induce euthyroid state. Each patient received 1200 mg of lithium carbonate in three divided doses. The study protocol included monthly monitoring of serum lithium, total serum T3, T4 and T3/T4 ratio, and a repeat radioactive iodine uptake (RAIU) at the end of three months. Twenty three patients completed the study. Of these, only 9 (39.1%) achieved euthyroid state, with a significant reduction in serum T3 and T4 but not in T3/T4 ratio and RAIU, suggesting a major effect of lithium on thyroid hormone release. No significant correlation was observed between serum lithium and circulating T3 and T4.