[en] Objective: To study the influence of hyperbaric oxygen on hypothyroidism after mi therapy. Methods: Fourty-two patients with early hypothyroidism after ¹³¹I therapy were randomly divided into two groups the hbo group (n=21) and the non-hbo group (n=21). Serum T₃, T₄4 and TSH levels were measured twice (four months apart) with CLIA in both groups. Results: Serum T₃ and T₄ levels were increased significantly in both groups after the four months course of low-dosage thyroid hormone replacement but there were no significantly differences between the final levels in the two groups (P>0.05). TSH levels were lowered significantly in both groups (both P<0.05), however, the magnitude of lowering was significantly larger in the hbo group than that in the non - hbo group (P<0.05). Conclusion: Hyperbaric oxygen therapy might be a potential useful means for treatment of early hypothyroidism after administration of ¹³¹I. (authors)