Bromhexine, 16 mg. 3-times daily, was compared with placebo in a double-blind crossover trial in 41 out-patients with chronic bronchitis and irreversible airways obstruction, and who were considered to be in a steady state. Each treatment was given for 3 weeks with a week of placebo in between; in addition, all patients took oxytetracycline, 500 mg. twice daily, starting 1 week before the trial and continuing throughout the duration of it. All patients completed the trial but the results from 5 were excluded because during the first 3 weeks they developed an influenza-like illness accompanied by a decrease in FEV1,and peak expiratory flow rate. Results from the remaining 36 patients showed a statistically significant reduction in phlegm stickiness (p smaller than 0.05) as judged by the patient, and a significant improvement in overall clinical state (p smaller than 0.05) as judged by the physician during bromhexine treatment, but no significant change in symptoms like cough, chest tightness, ease of breathing or sputum volume, peak expiratory flow rate and FEV1 etc. Five patients reported 6 side-effects, 3 with bromhexine, 1 with placebo and 1 with both treatments.