The trail pheromone of Nasutitermes is shown to be the cembrene analogue 12-isopropyl-1,5,9-trimethylcyclo-tetradeca-1,5,9-triene (10) by degradation, by comparison of its perhydro-derivative with perhydrocembrene, and by isomerisation with sodium methylsulphinylmethanide followed by degradation. The configurations of the double bonds are at present unknown. A key aspect of the work is the use of a quantitative micro-ozonolysis procedure.