The accuracy, reproducibility, and variability of seven commercially available peak flowmeters were assessed using the pulmonary waveform generator as recommended by the American Thoracic Society. The standard models were tested for peak flows of 100, 200, 320, 500, and 700 L/min. The low-range models were tested for peak flows of 80, 150, 200, 250, and 320 L/min. Most of the units provided highly repeatable estimates of peak now. However, the accuracy of several devices (Assess [Healthscan Products, Cedar Grove, NJ] and Mini-Wright [Clement Clarke International, Harlow, Essex, UK] low-range models, and the Ferraris [Ferraris Medical, Holland, NY] and Mini-Wright standard-range models) did not meet the National Asthma Education Program (NAEP) recommendations. The device with the best performance in terms of accuracy, variability, and reproducibility, and the only one in which all units tested met the NAEP recommendations, was the Astech (Center Laboratories, Port Washington, NY) full-range model.