Mitragyna inermis is used in the Senegal traditional medicine for treating stomach and intestinal disorders. At concentrations of 0.5, 0.75 and 1 mg/ml, the aqueous extract of M. inermis bark (AEMIB) significantly induced a decrease of the ileal basal tonus, respectively, from 37+/-1, 51+/-1 and 75+/-2% (P<0.05; n=5), compared to the baseline values. As well as atropine, AEMIB inhibited submaximal contractions induced by 0.01 mg/ml ACh with IC(50) value of approximately 0.75 mg/ml (n=5). These results show that AEMIB possesses both myorelaxant and antispasmodic actions in the ileum. This may justify the pharmacological basis for the popular use of Mitragyna for the treatment of gastrointestinal disorders.