In termites, soldiers play an important role in defense against predators, and have the specialized head morphology as weapons for defense. In derived termites subfamily Nasutitermitinae, soldiers possess frontal glands, from which chemical defensive substances are projected. Lots of genes, which are specifically expressed only in the soldier head of Nasutitermes takasagoensis, were isolated by the differential-display method. Because the soldiers perform the most specialized chemical defense, this result suggests that many genes are related to chemicals used for the defense. Among the soldier-specific gene candidates, northern blot and semi-quantitative RT-PCR revealed that the geranylgeranyl diphosphate (GGPP) synthase gene was highly expressed only in the soldier head. GGPP synthase is an essential enzyme for the synthetic pathway of GGPP from isopentenyl diphosphate, which is a precursor of all isoprenoid compounds. Although GGPP is used for the protein prenylation, which is ubiquitous in eukaryote, GGPP is a precursor of diterpene in many plants and bacteria. GGPP synthase of N. takasagoensis was expressed in single layer of secretory cells under the frontal gland reservoir that is thought to be a resinous diterpene synthetic site. It has been known that most components of the frontal gland secretions are resinous diterpenes in Nasutitermes. Consequently, we suggest that the GGPP synthase is related to the biosynthesis of defensive secretion in the nasute soldiers.