The effects of Ferula asafoetida gum extract on the contractile responses of the isolated guinea-pig ileum induced by acetylcholine, histamine and KCl, and on the mean arterial blood pressure of rat were investigated. In the presence of extract (3 mg/ml), the average amplitude of spontaneous contractions of the isolated guinea-pig ileum was decreased to 54 +/- 7% of control. Exposure of the precontracted ileum by acetylcholine (10 microM) to Ferula asafoetida gum extract caused relaxation in a concentration-dependent manner. Similar relaxatory effect of the extract was observed on the precontracted ileum by histamine (10 microM) and KCl (28 mM). However, when the preparations were preincubated with indomethacin (100 nM) and different antagonists, such as propranolol (1 microM), atropine (100 nM), chlorpheniramine (25 nM) then were contracted with KCl, exposure to the extract (3 mg/ml) did not cause any relaxation. Furthermore, Ferula asafoetida gum extract (0.3-2.2 mg/100g body weight) significantly reduced the mean arterial blood pressure in anaesthetised rats. It might be concluded that the relaxant compounds in Ferula asafoetida gum extract interfere with a variety of muscarinic, adrenergic and histaminic receptor activities or with the mobilisation of calcium ions required for smooth muscle contraction non-specificly.