Hexaprenyl pyrophosphate synthetase was detected in extracts of Micrococcus luteus B-P 26. During the course of purification the enzyme was resolved into two components, each of which had no catalytic activity but restored the hexaprenyl pyrophosphate synthetase activity when combined with each other. Both fractions, designated components A and B in the order of their elution from hydroxyapatite, were purified free of farnesyl pyrophosphate synthetase co-occurring in the same bacterium. They appeared to be proteins of molecular weights of approximately 20,000 (component A) and 60,000 (component B). Component A was more stable as compared with component B which was easily destroyed by relatively mild heat treatment. The hexaprenyl pyrophosphate synthetase reconstituted of these two components catalyzed the synthesis of all-trans-hexaprenyl pyrophosphate from isopentenyl pyrophosphate and all-trans-farnesyl or all-trans-geranylgeranyl pyrophosphate, but it did not catalyze a reaction between isopentenyl pyrophosphate and either dimethylallyl or geranyl pyrophosphate.