Abstract: On isolated isthmus of oviduct of the rabbit, Isocorydine (Isoc) (3μmol/L) decreased significantly the frequency of spontaneous contraction and muscle tensiori, but not the amplitude of contraction. The tension and frequency of spontaneous contraction can be suppressed by Isoc at concentractions from 3 to 300μmol/L. The amplitude of contraction was decreased only at 300μmol/L. It is suggested that the frequency and tension of spontaneous contraction of isthmic muscle are more sensitive to Isoc than the amplitude Isoc antagonized the norepinephrine—induced contraction of the oviduct. Thetransport of ova through the oviduct reduced by hCG could be delayed by Isoc.