Structures of eight new dimeric indole alkaloids of the ervafoline 1–4 and ervafolidine series 5–8, isolated from Stenosolen heterophyllus (Vahl) Mgf (Apocynaceae), were investigated by use of mass spectrometry, 1H and 13C nuclear magnetic resonance, and X-ray crystallography. A biogenetic pathway was proposed to take into account the formation of these unusual alkaloids, and, finally, a synthetic approach based on this proposal has been developed. © 1982, American Chemical Society. All rights reserved.