abstract the chemotype composition of achillea crithmifolia populations were studied in selfed and crossed progenies in order to gain information on their genetical background, with special respect to the main essential oil components: camphor, 1,8-cineole and borneol. distilled flower oils of individual samples of the original population, 36 self-pollinated progenies (1-1, 1-2, 1-3), 25 f-1 and 44 f-2 hybrid generations were analyzed by gc. camphor and borneol proved to be present in each sample, while 1,8-cineole was missing only in 0.17% of them. based on the results, a quantitative description of the main chemotypes (camphoraceous, cineolic and mixed) was given. in the established progenies, the proportion of the chemotypes varied according to the mother plants and breeding method. the segregation reveals that each of the mother plants possessed a heterozygotic structure for genes regulating the level of the main compounds. further, the same chemotype detectable as a phenotype might exist on the basis of a different genotypical background. the correlation system of the three monoterpenes was in harmony with these findings and the accepted biochemical models of their synthesis. it was concluded that a homogenous chemical constitution in the populations might be obtained only after several years inbreeding, and the examined compositional traits should be treated in breeding like quantitative features of polygenic determination.