In a chemotaxonomic survey of 380 taxa of Aloe, 20 species were found to contain the naphthalene derivative plicataloside as the major phenolic in the leaf exudate. Most of these species are restricted to East Africa (Kenya, Uganda and Tanzania). Only three species (A. chabaudii, A. palmiformis, A. plicatilis) in southern Africa contained this compound while the Malagasy endemics studied were found to be devoid of plicataloside. Macromorphology of the species was examined to search for other characters common to the species, and taxonomic affinities are assessed. Previous studies have suggested some of the taxa defined by this unique chemical compound to be taxonomically related, while many of the taxa have not previously been associated together.