In this study, the roots of Tabernaemontana heyneana Wall were examined and the isolation and identification of additional indole alkaloids and some pharmacological properties of coronaridine are described. Extraction of the roots yielded the alkaloids coronaridine, voacangine, ibogamine, 19-oxocoronaridine, and the pseudoindoxyl of voacangine. An acqueous ethanolic extract of the roots was found to prevent fertilization of adult female rats when administered orally. After the residue of this extract was treated chromatographic fractionation on silica gel yielded the alkaloid coronaridine. When administered to adult female rats, orally, coronaridine hydrochloride at levels of 5 mg/kg/day or above prevented pregnancy. Voacangine, assayed by the same procedure, did not prevent pregnancies. Data indicated that coronaridine was weakly estrogenic.