Peak flow meters are essential tools in the management of asthma. Many types are on the market. A computer-driven piston pump is normally not available for evaluation of the various meters. Comparison with values from a pneumotachograph is an accepted way of testing peak flow meters. This study aims at comparing 11 peak flow meters, for accuracy and linearity. Seven adult peak flow meters were tested: Miniwright with an equidistant scale (Clement Clarke); Personal Best (Healthscan); Wright Pocket fdE (Ferraris); Vitalograph (Vitalograph); Assess (Healthscan); Pocket Peak flow meter (Micro Medical); and Truzone (Monaghan). Furthermore, four low-range (LR) peak flow meters were tested: LR Miniwright with equidistant scale (Clement Clarke); LR Personal Best (Healthscan); LR Wright Pocket (LR Ferraris); and LR Pocket peak flow meter (LR Micro Medical). Two test series were performed: in the first one, a peak flow meter was connected downstream in series with a Fleisch #4 pneumotachograph. One subject performed 50 partial forced expiratory manoeuvres through this ensemble. In the second series, 50 adult patients and 25 healthy children performed sequential maximal forced expiratory manoeuvres on each peak flow meter, and on the pneumotachograph. A ranking system was devised for the various parameters of agreement of the meters with the pneumotachograph. Substantial differences in the quality of the adult meters were found. The adult peak flow meters with the closest agreement to the pneumotachograph were Personal Best and Micro Medical. In the low-range peak flow meters, the lowest differences were seen in the LR Personal Best and LR Micro Medical.