The eye findings of Graves' ophthalmopathy were prospectively recorded in 90 consecutive untreated patients (66 females, 24 males; mean age 44.5 years) according to the 1977 NOSPECS classification. Soft-tissue involvement was observed in 90%, proptosis greater than or equal to 23 mm in 30%, eye muscle involvement in 60%, corneal involvement in 9% and sight loss in 34%. No differences in the distribution of eye changes between right and left eye were found. Values for proptosis (mean +/- SD, 20.2 +/- 3.6 mm) had a near-normal distribution. Orbital computed tomography (CT) scanning (performed in 80 cases) demonstrated enlargement of inferior rectus in 60%, medial rectus in 50%, superior rectus in 40% and lateral rectus in 22%. Unilateral eye disease was present in 13 patients (14%); in 4 of these patients the CT scan showed eye muscle enlargement also in the fellow eye and in 2 patients bilateral eye disease subsequently developed. The distribution of age, sex and NOSPECS classes in patients with unilateral eye disease was similar to that in patients with bilateral eye disease, but the interval between the onset of thyroid and eye disease was much shorter in cases of unilateral than in cases of bilateral eye disease. Patients without clinically evident thyroid disease (n = 20, 22%) were not different from patients with thyroid disease in age, sex or ophthalmological presentation. The various data suggest: (1) the 1977 NOSPECS classification under-represents significant proptosis in 12% of cases; (2) the age and sex distribution of patients with Graves' ophthalmopathy is similar to that of cases with thyroidal Graves' disease, and (3) unilateral Graves' ophthalmopathy may represent an early stage of the disease, that as a rule already is or develops shortly afterwards into a bilateral disease.