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Warifteine, a bisbenzylisoquinoline alkaloid isolated from the root bark of Cissampelos sympodialis Eichl., produced a reversible, nonspecific and noncompetitive antagonism of histamine, carbachol and bradykinin induced contractions of the guinea‐pig ileum. The corresponding pD'₂ values (mean±SE) were 4.90±0.15, 4.95±0.20 and 5.03±0.11. Warifteine also antagonized oxytocin and bradykinin induced contractions of the rat uterus in a similar manner with pD'₂ values of 4.30±0.26 and 3.76±0.06 respectively. In the guinea‐pig trachea, the alkaloid inhibited spontaneous tone (IC₅₀, 1.1 × 10⁻⁵M) as well as carbachol induced sustained contractions (IC₅₀, 2.9 × 10⁻⁵M). As warifteine antagonized KCI induced contractions of the guinea‐pig ileum (pD'₂ value 4.57±0.10), inhibition of Ca⁺⁺ influx through voltage operated Ca⁺⁺ channels may be partially responsible for its antispasmodic activity. However, the …