The aim of the present study was to investigate the antispasmodic effect of the total extract of Achillea nobilis L. subsp. sipylea (Schwarz) Bassler (Asteraceae) on rat duodenum. In the first part of experiments, cumulative dose-response curves for acetylcholine (Ach) were obtained and then dose-response curves are repeated after addition of atropine, papaverine and different doses of the extract. In the second part, cumulative dose-response curves to CaCl2 were obtained in the absence and presence of verapamil and different doses of the extract. In the third part, papaverine and extract were applied to the tissues after contraction with K+. The extract has exhibited an inhibitory effect on the dose-response curves induced by Ach and CaCl2 on rat duodenum and significantly reduced the maximal response in a concentration-dependent manner. A similar effect was observed with papaverine but not with atropine on the dose-response curves obtained by ACh. Verapamil also reduced the maximal response in curves induced by CaCl2. The present results demonstrate that total extract of A. nobilis subsp. sipylea exerts antispasmodic activity on rat duodenum. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.