This paper gives first an outline of the taxonomy of indigenous and endemic Strychnos species of Madagascar and describes their ethnopharmacology with focus on their ethnomedical uses as herbal remedies to enhance chloroquine action during the sudden emergence of malaria in Madagascar in 1980's. This led to the discovery of the chemosensitizing activity of the new Nb-C(21) secocuran Strychnos alkaloids. The alkaloid content of Strychnos species are reviewed and their chemotaxonomy briefly described. The second part of the paper reports new NMR strategies for structure elucidation, exemplified by structure analysis of monoindole and bisindole alkaloids published during the period 1994-2000. The third part of the paper reports the biological activities of Strychnos alkaloids reported over the same period with emphasis on the chemosensitizing effect of the Nb-C(21) secocuran alkaloids. © 2002 Elsevier B.V. All rights reserved.