Asthma is now recognized as a serious occupational disease. The symptoms and diagnosis of asthma are described. Common occupational sensitizers in the arts include nickel, epoxy resins, fiber-reactive dyes, formaldehyde, chromates and dichromates, platinum and gold salts, western red cedar and many tropical woods, Plexiglas, dust, rosin and rosin soldering fumes, and isocyanates. Asthma is distinguished from bronchitis and other responses to irritants, and its development and possible treatments are described.