Nine patients with Graves' ophthalmopathy (GO) were treated with intravenous methylprednisolone pulse therapy and followed up by ophthalmological assessment, magnetic resonance imaging, and thyroid-associated autoantibody (thyroid stimulating antibody (TSAb), TSH binding inhibitor immunoglobulins (TBII), and anti-eye muscle antibody (EMAb)). Ophthalmological assessment was performed by the ophthalmopathy index (OI) which was made on the basis of the system recommended by the American Thyroid Association Committee. EMAb was expressed as the ratio of density of the 64 kDa band of eye muscle membrane to that of 92 kDa non-specific band found with all normal sera when assessed by western blotting. Five patients with mild ophthalmopathy (OI < 4) did not show progressive improvement in OI. Three of 4 patients with severe eye disease (OI > 4) showed a progressive and distinct improvement in OI. These 3 patients had high TSAb levels before methylprednisolone pulse therapy. One patient with severe ophthalmopathy did not respond to this pulse therapy; this patient's TSAb was negative. A significant positive correlation was observed between the activity of TSAb before treatment and the improvement in OI (delta OI) (r = 0.86, P < 0.01, n = 9). The relationship between delta OI and EMAb did not reach significance. These results suggest that TSAb in sera of GO patients can be a useful marker for predicting the efficacy of methylprednisolone pulse therapy.