Twenty-two patients with Graves' ophthalmopathy underwent biopsy, and two patients had both eyes biopsied. The samples for the control group (n = 4) were obtained during routine non-thyroid-related corrective strabismus surgery. Ophthalmological evaluation with clinical activity score (CAS), endocrinological evaluation, and ultrasound were used in our study. Correlation between clinical and histological analyses in connective tissues and extraocular muscles from patients with Graves' ophthalmopathy was done. The echography results disclosed an enlargement in all extraocular recti muscles with the exception of one patient. Periodic acid-Schiff and Giemsa stains revealed a moderate number of mast cells in the endomysial connective tissue, none of which displayed significant degranulation. There were no signs of muscle cell damage. Fifteen of the biopsies showed weak cellular reactions with only scattered inflammatory cells. Furthermore, the inflammatory process may be localized and not equally distributed throughout the muscle. Thus, the biopsies might not be representative for the whole muscle. Statistical significance analysis was found when sex and CAS were compared (p = 0.001683) using the Fisher Test. In conclusion, our investigation indicates a pleomorphic pattern of histologic findings in connective tissue and extraocular muscles in Graves' ophthalmopathy.