Previous studies have shown that suggestion may modify bronchial reactivity to both inactive diluents and pharmacologically bronchoconstrictor or dilator substances. In our study, 14 patients were subjected to two methacholine challenge tests presented, respectively, as a bronchoconstrictor or as a bronchodilator drug. Forced expiratory volumes in one second were recorded and a PD20 was determined. No significant differences were reported in PD20 values of each patient after the two kinds of suggestion.