The technique by which human bronchiolar strips are prepared is described in detail. The biological viability of the preparations after storage at 4 degrees C overnight and the reproducibility of contractile responses to KCl and methacholine were examined in lung tissue from six patients. Measurements were performed on the first and second day after surgical resection. On both days, most bronchioles showed an increase in contractility. The responses on the first day were not different from those on the second day. No significant changes in time were found for pD2 and slope of the methacholine dose-response curves. The variability of responses between patients was significantly larger than between strips within patients. The pD2 was the best reproducible parameter.