A new chemotype (C type) ofPerilla frutescens(Labiatae) that accumulatestrans-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 F1and F2progenies showed thattrans-citral is accumulated when its metabolism is blocked in the simultaneous absence of a dominant geneN, which is involved in the conversion oftrans-citral into naginataketone viacis-citral, and two polymeric genesFr1andFr2, which are involved in the conversion oftrans-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 inPerillahave been revised.