The tolerability of 57 non-smoking asthma patients inhaling salbutamol as needed (ATS, 18--60 years, 60% < or = FEV1 < or =100%, PD15FEV1 <0.4 mg histamine) to fibreoptic bronchoscopy (FOB) and endobronchial biopsy was studied. The FOB was done in local Lignocaine anaesthesia, and from five to eight biopsy specimens were taken from the bronchial mucosa of the right lung. The tolerability was measured as cough/bronchospasm during the procedure (from 0 = normal to 3 = interrupted procedure), success of the procedure, and untoward occurrences. Twenty-seven of the 57 patients (48%) had no cough or bronchospasm during the FOB (score 0). Few coughs of no importance (score 1) were documented in 23 patients (40%). Seven patients (12%) had cough and/or bronchospasm interfering with the FOB procedure (score 2). The FOB procedure was not interrupted because of cough and/or bronchospasm (score 3) in any patient. Scores of cough and/or bronchospasm diminished progressively with the increase of PD15FEV1 histamine. The success of the procedure was 100%. Two patients had untoward medical occurrences requiring additional rescue medication (3.5%). In conclusion, we found that hyperreactivity predicts cough and/or bronchospasm during the FOB. Cough and/or bronchospasm are frequently observed during the bronchial procedure, but they are mild and of minor clinical importance. An investigational endobronchial procedure can be successfully performed in mildly or moderately obstructive asthmatic patients, even in cases with severe bronchial hyperreactivity.