Background: With the availability of compact, portable, effective microspirometers, pulmonary function tests no longer need to be performed only in specialized laboratories. However, the perception persists that small flow-sensing devices are less accurate than volume-sensing spirometers. Objectives: To study the accuracy of spirometry performed with the MIR Spirobank® and to investigate how accurately trained primary-care physicians can perform spirometry using a portable electronic spirometer. Methods: Patients with suspected occupational asthma were submitted to specific bronchial challenge tests in the pulmonary function laboratory according to published recommendations. Serial measurements were performed with the Jaeger MasterScope device (reference standard) or the Spirobank device. Data were generated from 908 parallel measurements on 34 patients. Furthermore, 16 patients with documented moderate to severe COPD were examined in a carousel set-up by four trained physicians who each used his/her own Spirobank device coupled to a laptop computer. Results: The Spirobank spirometer performed very well compared with the Jaeger MasterScope in a laboratory environment, displaying an underestimation of the forced expiratory volume in 1 s (FEV(1)) and FEV(1)/forced vital capacity (FVC) of 2-5%. High correlations were found for the pulmonary function parameters. The highest correlation was for FEV(1) (r(2) = 0.949) and the lowest for the maximum expiratory flow at 25% of FVC (MEF(25)) (r(2) = 0.864). Only 2% of the observed variation in the measurement results could be explained by the type of device. Conclusions: The Spirobank device seems to be appropriate for research purposes if the standardized protocol is used correctly and the acceptability criteria are respected.