Three selfing and 13 crossing experiments between tetraploid individuals of Achillea ceretanica. Achillea collina, Achiliea distans ssp. 'styriaca' Saukel lined.), and Achillea pratensis (Achillea millefolium complex. Compositae), five Fl crosses, three backcrosses and one further selfing experiment were carried our in order ro study the inheritance of longipinenone (1) and its hydroxyl derivative (2). From these crossings, 1294 plants were studied by qualitative thin layer chromatography. Progenies from parent and Fl plants without longipinenones (0-type, ll) uniformly contained none of these two sesquiterpenes. All other crossing experiments showed typical segregation patterns of 0-type, L-type (longipinenone ii) without hydroxy-longipinenone, L.hh) and H-type (hydroxy-longipinenone (2) and occasionally longipinenone. L.H.) in the ratio of 1:1 and 1:3. According to these results both derivatives are under dominant genetic control regulated by gents L. and H, whereby hydroxylation takes place after synthesis of longipinenone (1).