Organizing pneumonia associated with textile dye spraying in Valencia, Spain was described, and an epidemiological study of the outbreak was reported. There were six deaths. Employees (257) were interviewed with regard to respiratory symptoms, smoking habits, and duration and characteristics of employment at eight factories. In 71 of the 257 (27.6%) there were one or more of the following findings: respiratory symptoms not attributable to any other evident disease, abnormal chest radiograph (CXR), abnormalities of lung function or intraalveolar fibrin knots or organizing pneumonia in lung biopsy. There were 22 workers who fulfilled the case definition. There was an overall attack rate of 8.9%; the attack rate was highest in factory-A at 27.2%. Only two of the 22 cases had not worked in factory-A or factory-B. The risk of being a case was higher among the sprayers and cleaners whose work involved direct contact with the aerosol products than those employed in other tasks. In four cases the symptoms began 1 month after entry to the factory. Results of an investigation of products used at the factories indicated that the pulmonary disease was caused by the inhalation of an aerosol from a process modified by the substitution of Acramin-FWN for Acramin-FWR, and the substitution of a solvent for water, accompanied by the application of the product as an aerosolized spray.