General agreement has emerged that the perceptions of patients of how they are feeling and how they are able to function in daily life should be included in the evaluation and monitoring of the effects of disease and treatment. Thyroid-associated orbitopathy (TAO), an inflammatory autoimmune eye disease, affects 50%-60% of patients with Graves' hyperthyroidism. Having blurred vision and/or diplopia has a detectable and significant impact on functional status and well-being, especially in role limitations caused by physical health problems. Therefore, to assess the impact of TAO on quality of life, we performed a descriptive study on consecutive ophthalmopathy patients with varying degrees of severity of TAO. General quality of life was assessed using a brief, internationally accepted, and standardized general questionnaire: the Medical Outcomes Study (MOS-36). In comparison to a large German reference group, low scores on the MOS-36 were found. Marked and significant differences from the control group were especially observed for the following items: vitality, social functioning, mental health, health perceptions, and body pain. MOS-36 did not correlate with the duration or severity of the ophthalmopathy. These results demonstrate the impact of a common visual symptom on health status and well-being, as measured by the MOS-36. In addition, comparison of the impact of various symptoms and conditions provides important and potentially clinically relevant information. In conclusion, we have shown that TAO has a large influence on the quality of life of these patients. The negative impact on well-being seems not to be related to the usual clinical assessment. These findings underscore the need for quality of-life measurements in prospective and controlled clinical trials.