Genetic control of volatile oil production inAgastache foeniculumand, more specifically, of the production of myrcene, limonene, and methyl chavicol, three major components of its essential oils, was elucidated. Controlled crosses were made between individuals with different chemotypes, and F2populations were analyzed for their composition of volatiles by using headspace gas chromatography. Total aromatic volatile emittance was found to be under polygenic control with additive gene effects for four of eight families studied, and each of the three major components was controlled by one to a few genes with recessive to additive effects. Evidence is also presented suggesting that population PI 561057 transmits a genetic factor or factors that suppress the overall production of the major volatile oil components.