Ten different plants of wormwood were collected in March 1997 from each one of the following four wild populations in the Spanish Pyrenees: Tallo de Aulet (prov. Huesca) and Pont de Suert, Sort and Farga de Moles (prov. Lleida). In three of the four populations studied, there was another chemotype, with 25-65% of cis-epoxyocimene and 15-50% of chrysanthenyl acetate. This chemotype, called chemotype B, was less frequent in the Pyrenees than the chemotype A, appearing only in 17% of the samples (two samples in TallO de Aulet and in Pont de Suert and three samples in Farga de Moles).

Two chemotypes were detected; a cis-epoxyocimene type (with more than 50% of this compound) which was predominant in all the populations, and a cis-epoxyocimene + chrysanthenyl acetate type (with 25-65% of cis-epoxyocimene and 15-50% of chrysanthenyl acetate). The distribution of these chemotypes had no relation with the altitude of the samples.