The rheological behavior and clearance of bronchial mucus samples collected by protected expectoration from 24 out-patients with simple chronic bronchitis were investigated before, at the end of a short period of treatment (4 days) with a single oral dose of 2.7 g (sachet) of carbocysteine-lysine (evening meal), and on the 4th and 8th days after the end of treatment versus placebo. In the group treated with carbocysteine-lysine, there were significant reductions in viscosity (-67, -48, -62%) and increases in mucociliary transport (+41, +31, +34%) at the three times mentioned. The most striking finding was that the improvements were still present 8 days after cessation of treatment. The elasticity parameter was not affected in any statistically significant way (-10, -24, +65%). These findings suggest the presence of some type of 'post-mucoactive' effect.