The terpene trilactone content (bilobalide and ginkgolides) of extracts prepared from leaves of terminal buds, rosettes and side branches, from stem and root bark, and from root and root meristems of three-year-old Ginkgo biloba plants was determined. The aerial parts were relatively rich in bilobalide while ginkgolides were the major constituents of the underground parts. The formation of farnesyl and geranylgeranyl pyrophosphate was monitored by incubating cell-free extracts prepared from the corresponding plant parts with [1- 1 4 C]isopentenyl pyrophosphate. Extracts prepared from leaves of the terminal buds displayed terpenoid biosynthetic activity, suggesting that terpene trilactone synthesis might occur in actively growing tissues.