Purpose: To investigate the value of magnetic resonance imaging (MRI) in the determination of the fibrotic phase in dysthyroid orbitopathy, which may be an indication for early surgery. Patients and Methods: Thirteen patients with dysthyroid orbitopathy who had vertical deviation in excess of 20 PD and associated diplopia in the primary position that did not respond to medical treatment were included in the study. On MRI, the absence of high-intensity foci in the T2 sequence, especially in the coronal planes, indicated that the extraocular muscles were not edematous. These muscles were evaluated as being in the fibrotic phase, and surgery was performed without waiting the recommended 6 months for the stabilization of the angle of deviation. Results: The complaint of diplopia disappeared after a single operation in 8 patients, and after a second operation in 4. Thus, success was obtained in 12 of the 13 patients. One patient with persistent vertical diplopia refused a second operation. Conclusion: Our results indicate that MRI is an effective and reliable method for the determination of the fibrotic phase in patients with dysthyroid orbitopathy who have diplopia in the primary position, and that MRI results have an important role in determining whether early surgery is appropriate.