Alkamides are the major lipophilic constituents of Echinacea angustifolia roots. Due to their structural similarity with anandamide, we have evaluated their ability to bind to rodent cannabinoid receptors CB1 and CB2 by a standard receptor binding assay using [(3)H]CP-55,940 as a radioligand. The alkamides exhibited selective affinity especially to CB2 receptors and can therefore be considered as CB ligands. Most of the alkamides showed good metabolic stability as indicated by the similarity between affinity to CB1 determined in the presence/absence of the protease inhibitor PMSF. It is suggested that CB2 interactions may be the molecular mode of action of Echinacea alkamides as immunomodulators.