purpose 1) To test the short- and long-term efficacy of Methylprednisolone Pulse Therapy (MPT) for patients with Dysthyroid Optic Neuropathy (DON). 2) To assess possible side-effects of MPT. 3) To assess whether a delay in decompressive surgery would influence the visual outcome. study design Retrospective, uncontrolled. method The records of 62 consecutive patients with DON, who received MPT between 1994 and 2000, were evaluated with special attention for pre- and post treatment ophthalmic and orthoptic parameters, Clinical Activity Score (CAS), visual fields and visual evoked potentials, and treatment complications. DON-patients were hospitalized and received four times 500 mg methylprednisolone intravenously. Immediately afterwards they were treated with oral prednisone (maximal dose 60 mg) and/or orbital irradiation (10 times 2 Gy). Evaluation was done one day after the last bolus (T1) and when the orbitopathy had been stable for at least six months (T2). results Visual acuity, proptosis, elevation and CAS all improved significantly at T1, whereas the lid aperture did not change. At T2, 24 out 62 (39%) DON-patients were stable with normal vision. The other 38 (61%) had undergone orbital decompression because of persistent or recurrent DON within one week to six months after MPT. Final visual acuity in the whole group (121 eyes) was less than 0.1 in 3 eyes, between 0.1 and 0.5 in 17 and more than 0.5 in 101 eyes. Treatment complications were: pylorus ulcer (n = 1), increased osteoporosis (n = 1), abcess formation (n = 1), and increase in insulin dosage (n = 1). conclusions 1) MPT is efficious as emergency treatment. 2) One-third of DON-patients are spared decompressive surgery. 3) MPT causes only rare and no serious side-effects. 4) The final visual outcome after MPT and orbital decompression is comparable to the results of immediate decompression.