A randomized double-blind cross-over study compared the clinical effectiveness of a 14-day treatment with 400 mg X day-1 of sobrerol and placebo in 23 patients with stable chronic bronchial disease. During the seven week trial, subjective symptoms and findings (cough frequency and severity, difficulty in raising sputum, dyspnoea) were recorded, pulmonary function tests performed and sputum physical characteristics (24-h sputum volume, purulence, cell concentration, protein, sputum dry weight and "apparent" viscosity) determined on a regular basis. Side-effects were closely monitored. Both subjective assessment of overall clinical efficacy as well as statistical analysis of the above mentioned factors failed to show any significant advantage of sobrerol to placebo--except for a transient decrease of the 24-h sputum volume. Sobrerol appears to be another example of an expectorant lacking evidence of clinical effectiveness in the management of chronic bronchial secretions.