To determine the clinical characteristics of an incidence cohort of patients with Graves' ophthalmopathy. We reviewed the community medical records of 120 patients residing in Olmsted County, Minnesota, in whom Graves' ophthalmopathy was diagnosed between 1976 and 1990. Among 120 patients with Graves' ophthalmopathy, 108 (90%) patients had Graves' hyperthyroidism, one (1%) had primary hypothyroidism, four (3%) had Hashimoto's thyroiditis, and seven (6%) were euthyroid. At some point in their clinical course, eyelid retraction was present in 108 patients, whereas the approximate frequency of exophthalmos was 62% (73 patients); restrictive extraocular myopathy, 43% (51 patients); and optic nerve dysfunction, 6% (seven patients). Only six (5%) patients had eyelid retraction, exophthalmos, optic nerve dysfunction, extraocular muscle involvement, and hyperthyroidism. At the time of diagnosis of ophthalmopathy, upper eyelid retraction and eyelid lag were documented in 85 and 52 patients, respectively, and the most frequent ocular symptom was pain (36 patients, 30%). Diplopia was noted at the initial examination by 20 patients, lacrimation was present in 25 patients, 19 patients had photophobia, and nine patients had blurred vision. Decreased vision from optic neuropathy was present in less than 2% of eyes at the time of diagnosis. Thyroid dermopathy and acropachy accompanied Graves' ophthalmopathy in five patients (4%) and one (1%) patient, respectively. Myasthenia gravis occurred in only one patient. Eyelid retraction is the most common clinical sign of Graves' ophthalmopathy. The complete constellation of typical features (hyperthyroidism, eyelid retraction, exophthalmos, restrictive extraocular myopathy, and optic nerve dysfunction) occurs relatively infrequently.