Chloroplasts isolated from fully developed spinach leaves and incubated in the presence of isopentenyl pyrophosphate were able to synthesize rapidly geranylgeranyl chlorophyll alpha and geranylgeraniol. The biosynthesis of the geranylgeraniol derivatives from isopentenyl pyrophosphate is a compartimentalized process. The membrane fractions (thylakoid and envelope membranes) were essentially unable to synthesize geranylgeraniol, geranylgeranyl pyrophosphate and geranylgeranyl chlorophyll alpha. When stromal and thylakoid fractions were combined the capacity to synthesize geranylgeranyl chlorophyll alpha and geranylgeraniol was restored. When stromal and envelope membrane fractions were combined the capacity to synthesize gernylgeranyl pyrophosphate and geranylgeraniol was restored. The products of the reaction were discharged inside the lipid phase of the membranes.