With the advent of small inexpensive peak flowmeters, the at-home monitoring of peak flow rates has become an invaluable aid in the treatment of asthmatic patients. In this study, we evaluated the performance of the MiniWright and Assess peak flowmeters for accuracy and reproducibility. Measurements were made at varying peak flow rates and compared with those obtained simultaneously by a calibrated pneumotachograph. When this segment of the study was completed, the peak flow devices were subjected to 200 uses and were then retested. Four MiniWright peak flowmeters that had been extensively used in our clinic were tested as well. The Assess peak flowmeter was more accurate than the MiniWright at low flow rates (less than 300 L/min), while the MiniWright meter was more accurate at high flow rates (greater than 400 L/min). We also found that the accuracy of the MiniWright meter deteriorated after 200 uses and worsened further after extensive use, while the Assess meter retained its accuracy after 200 uses.