Instruments currently used in spirometry were discussed. The quality and sophistication of spirometric instruments have improved in recent years. These improvements have been stimulated in part by recommendations of the American Thoracic Society (ATS) and in part by the advent of relatively fast, portable, and inexpensive computers that enabled production of automated instruments. The availability and quality of spirometer test equipment and mechanical pumps have also improved. The relative advantages and disadvantages of flow and volume spirometers were considered. Changes in standards for spirometry instruments were discussed. The discussion included summaries of ATS recommendations for spirometry instruments made in 1979 and 1987. The 1979 standards included guidelines for equipment design, quality control, maneuver performance, measurement procedures, and test acceptability and reproducibility criteria. The 1987 recommendations were updates of the 1979 standards that included adoption of 24 standard waveforms, an environmental conditions statement, lowering the extrapolated volume limit from 10 to 5% of forced vital capacity (FVC), and changing the end of test criterion. Recent advances in spirometry hardware and software were described. These included programs that enable computerized assessment of test acceptability and reproducibility with immediate feedback to the technician and development of a small portable spirometer that can measure 1 second forced expiratory volume, FVC, and other parameters.