Aim of the study was to discover whether the recovery phase after methacholine challenge might be influenced by the administration of an antimuscarinic drug and to verify the mode and timescale of restored receptor activity. 16 patients with severe bronchial hyperreactivity were selected and subjected to methacholine test in order to assess: the preventive bronchodilatory effect of ipratropium bromide (40 mcg) inhaled before the test and the bronchial spasm spontaneous recovery after PD20 at 15, 30 and 60 minutes. Data were subjected to variance and Tukey test analysis. The results confirm that ipratropium bromide raises the methacholine dose response threshold by a factor of about 10 and also demonstrate that the anti-muscarinic drug modified the FEV1 PD20 and influenced the recovery phase by intensifying and making the bronchial spasm resolution faster. Thus results moreover suggest that the receptor activity restoration depends also on the elimination of the muscarinic mediator.