Twenty alkaloids were isolated from the aerial parts of Melodinus hemsleyanus Diels. Fifteen of them were known, viz., tabersonine, 11-methoxytabersonine, 11-hydroxytabersonine, 11,19R-dihydroxytabersonine, 11-hydroxy-14,15-α-epoxytabersonine, scandine, 10-hydroxyscandine, meloscine, meloscandonine, venalstonine, venalstonidine, vindolinine, picralinal, picrinine and akuammidine. The other five alkaloids were new. Their structures were established as 11-hydroxyvincadifformine, 14,15-epoxyscandine, 19-epimeloscandonine, 16β-hydroxy-19R-vindolinine and 16β-hydroxy-19S-vindolinine by means of spectroscopic and chemical methods. A pharmacological test revealed that 11-hydroxyvincadifformine has significant antifertility activity. © 1993.