BACKGROUND: The NIOSH Spirometry Training Guide is based on two earlier publications, the NIOSH Spirometry Workbook and the NIOSH Manual of Spirometry in Occupational Medicine. In the new curriculum, the material covered in the NIOSH Manual of Spirometry in Occupational Medicine has been simplified and incorporated into the content of the NIOSH Spirometry Workbook. New material has also been added, including a comparison of volume and flow spirometers and volume/time and flow/volume tracings, quality assurance procedures, occupational lung diseases and hazards, and information from the American Thoracic Society Standardization of Spirometry--1994 Update. The American Thoracic Society is the medical section of the American Lung Association. It has provided a leading thrust in the standardization and upgrading of spirometric instruments and practices. Its first set of standards, ATS Statement--Snowbird Workshop on Standardization of Spirometry was essentially incorporated by OSHA in the Cotton Dust Standard, which was promulgated on June 23, 1978. The Snowbird Workshop standards were revised in 1987 (2), and again in 1994, and released as the ATS Standardization of Spirometry--1994 Update. PURPOSE: The NIOSH Spirometry Training Guide was prepared for use as an adjunct or supplement to a NIOSH approved course on spirometry. It is not intended to serve as a self-instructional package. Learning spirometry requires observation, demonstration, and hands-on practice. INTENDED AUDIENCE: This Guide is intended for individuals who are responsible for conducting spirometry in the workplace. It will be of special interest to occupational health physicians, nurses, and other health professionals.