The repeatability of a rapid dosimetric method for methacholine challenge was evaluated with 11 asthmatic patients. A Spira Elektro 2 dosimeter was used for methacholine delivery and a pocket turbine spirometer (Micro Spirometer) for FEV1 measurements. Methacholine was delivered in four successive, increasing doses ranging from 80 micrograms up to a cumulative dose of 6900 micrograms. The single determination standard deviation was low (12.5%), corresponding to a 95% confidence interval of +/- 0.925 doubling doses. The mean difference (+/- SE) between measurements of log PD20 FEV1 was -0.015 (0.056), and the absolute value of the difference in log PD20 FEV1 was not significantly related to the average log PD20 FEV1 (r = -0.155, P = 0.65). The rapid dosimetric methacholine challenge test, performed with a pocket turbine spirometer, proved to be as reproducible as previous methods. Furthermore, this methacholine challenge is clearly less time consuming than conventional provocations, including bronchodilator aerosol (given to resolve post-challenge bronchoconstriction); the whole test can be performed in 20 min. This is especially valuable in epidemiologic studies, as well as in clinical practice.