The engineering of terpenoid formation in plants, although highly appe
aling from a biotechnological viewpoint, is particularly challenging b
ecause of the myriad of terpenoids produced from a single intermediate
(isopentenyl diphosphate) and the complex organization and subtle reg
ulatory features of the biosynthetic pathways. This article surveys ma
ny of the biochemical issues that must be appreciated before attemptin
g to develop rational strategies for the bioengineering of terpenoid b
iosynthesis.