Abstract: Effects of osthole (Ost) anti verapamil (Vet) were investigated in the isolated guinea-pig ileum and taeniae coli. In the isolated guinea-pig ileum or taeniae coli, Ost and Vet were both found to inhibit the contractions induced by acetylcholine(ACh), histamine (His) and KCl in a dose-dependent manner; and noncompetitively antagonize the CaCl₂ cumulative dose-response curves, with pD₂ values of 4.41±0.15 and 7.0±0.2, respectively. Ost at dose of 100 μmol/L and Ver at 1 μmol/L inhibited CaCl₂ 0.2 mmol/L induced the contractions of the isolated guinea-pig taeniae coli. and the contractions can be abolished by adding CaCl₂ 2 mmol/L in Ca²⁺-free medium; both of them showed pronounced inhibitions on intracellular calcium-dependent contractions induced by ACh, but showing no effects on the extracellular calcium-dependent contractions. These results indicate that Ost has calcium antagonistic effect and is similar to Vet in mechanism.