This article discusses the problem of assessing disability from occupational asthma using the American Medical Association (AMA) Guides, entitled the Guides to the Evaluation of Permanent Impairment, Third Edition, published by the AMA. The AMA Guides treat occupational asthma as a special case or subset of respiratory impairment assessment, but do not develop an entirely separate evaluative process. The Guides provide a clear criterion for determining if asthma is actually present and also indicate a mechanism to categorize the physiologic impairment due to the asthma. The Guides approach impairment assessment based on physiologic function rather than etiology; the exact cause of the air flow obstruction is less important than the physiologic effect. Legally imposed considerations, such as apportionment of the illness to occupational versus nonoccupational causes are not addressed by the AMA Guides. The Guides cover the diagnosis of asthma, determination of the extent of impairment, treatment, and job specific disability.