The petroleum ether/Et,O extract of the underground parts of Achillea wilbelmsii afforded 13 novel alkamides. Their structures and stereochemistries were determined by spectroscopic methods. The general pattern is characterized by derivatives with highly unsaturated acid moieties with different carbon chain lengths. The C, amides predominate, and smaller amounts of C,4 derivatives are observed. This species is particularly characterized by the accumulation of isopentyl amides that represent a new type of alkamide. The genus Achillea is characterized chemically by the frequent accumulation of olefinic and acetylenic alkamides, a biogenetic capacity that it shares with some other genera of the Compositae-Anthemideae as well as with members of the Compositae-Heliantheae. Besides the more widespread isobutyl and phenethyl amides, the occurrence of compounds with cyclic amide moieties is confined to the tribe Anthemideae (1). As shown in preceding articles, Achillea species are especially rich in piperidides, pyrrolidides, and the corresponding dehydro derivatives (piperideides, pyrrolideides) (1-4). More recently, a series of hitherto unknown pyrrolides has been isolated from Achillea ageratifolia (Sibth. & Smith) Boiss. (5). Apart from the different amine parts, trends towards different carbon chain lengths and stereochemistries as well as different levels of unsaturation within the acid residues have been shown to serve as additional chemotaxonomic criteria within Achillea ( 1,4,5).