A case of Graves' ophthalmopathy, ocular myasthenia gravis (MG) and Hashimoto's thyroiditis is presented, an association that has not been previously reported. A 22-year-old woman presented with exophthalmos and a normal-sized thyroid. Four years later, shortly after delivery of her second child, ocular MG developed. Twenty years after her initial symptoms, Hashimoto's thyroiditis and mild hypothyroidism were diagnosed. Treatment of the latter brought about marked improvement of the ophthalmoplegia. The differential diagnosis of ophthalmoplegia is discussed, and the importance of recognizing and treating hypothyroidism in MG is emphasized. Since Hashimoto's thyroiditis as well as MG have an abnormality of T-lymphocyte regulatory function, and the autoimmune process is directed in both diseases against cell membrane receptors, they can be considered as pathogenetically related. The reported case exemplifies this association.