A new chemotype (C type) of Perilla frutescens (Labiatae) that accumulates trans-citral as a main component of the essential oil in the leaf was crossed with five other chemotypes containing perillaldehyde (PA), elsholtziaketone (EK), perillaketone (PK), perillene (PL), and phenylpropanoid (PP) as their respective major components for comparison of genetic differences. The analyses of F1 and F2 progenies showed that trans-citral is accumulated when its metabolism is blocked in the simultaneous absence of a dominant gene N, which is involved in the conversion of trans-citral into naginataketone via cis-citral, and two polymeric genes Fr1 and Fr2, which are involved in the conversion of trans-citral into perillene. On the basis of new data obtained from various intercrosses involving the C type as one of the parents, the genotypes of different chemotypes as well as the sites of action of several genes controlling reaction steps in the biosynthesis of monoterpenes in Perilla have been revised.