The bronchospasmolytic, antiallergic, anti-inflammatory, mucolytic and antitussive activities of 8-(2-phenylethyl)-1-oxa-diazaspiro[4,5]decan-2-one 2-tiophenecarboxylate (decasilate, CAS 76652-72-7) have been evaluated using different experimental models. 1. Decasilate showed a remarkable spasmolytic activity against histamine-induced contractions in the isolated guinea-pig tracheal preparation with an IC50 of 2.7 x 10(-6) mol/l. In addition, the oral administration of decasilate (5-30 mg.kg-1) significantly reduced the histamine aerosol-induced bronchospasm in guinea-pigs. 2. Decasilate had a preventive effect against antigen-induced contractions of ileum segments from sensitized guinea-pigs (EC50 8.0 x 10(-6) mol/l) and relaxed them when added after the antigen challenge (IC50 9.5 x 10(-7) mol/l). 3. Both carrageenin- and dextran-induced rat hind paw oedemas were significantly reduced by the oral administration of decasilate with ED50 values of 169.5 and 34.5 mg.kg-1, respectively. However, it was ineffective against the cotton pellet-induced granuloma in the rat. 4. Furthermore, decasilate had a significant mucolytic activity in rabbits and reduced the number of tussive seizures induced by an aerosol of citric acid in guinea-pigs. The pharmacological profile of decasilate suggests that it might be useful in the management of chronic bronchitis.