The clinical testing of trans-4-[(2-amino-3,5-dibromo-benzyl)amino]cyclohexanol-hydrochloride (ambroxol, NA 872) in surgical patients was carried out over a period of 7 days. Regular application of 60 mg/day showed a clear improvement in subjective symptoms, particularly in cases of bronchitic syndrome. In some patients improvement could be demonstrated objectively by means of sputum viscosimetry. The clinical effect is principally one of facilitation of expectoration and fluidification of mucus, which often prior to therapy is rather viscous. This leads to a favourable influence of the post-operative treatment period. As a rule the substance is well-tolerated. The recommended dose of the drug for the average treatment is 2 ampoules/day i.v. (30 mg) and a single to twice daily inhalation of 2 ml (15 mg) for 5--7 days post-operatively.