SummaryCardiotonic drugs are classified in two groups : 1) heterosides, and 2) alca-loids.Theheterosidesinclude cardenolides and scilladienolides. The chemical structure of each drug is shown as well as the relations between the various compounds presented.Thealcaloidsinclude 1) substances with phenanthrene nucleus extracted from Erythrophleums, 2) indolic alcaloids isolated from Voacanga. These alcaloids are still in the experimental stage of pharmacological investigation.