Previously, in boron subphosphide B 12 P 2 synthesized by the same self-propagating hightemperature method we have discovered two systems of twins i.e. conventional twins on the (0003) h plane and nanotwins resulting from duplication of the rhombohedral unit cell of B 12 P 2 along one of the basic vectors . In the present study, neither these nor other twins were observed in the only few B 12 P 2 particles found. The latter can be explained by the fact that B 12 P 2 is a secondary phase formed due to the thermal decomposition of as-synthesized BP at points of the local overheating in the reaction front.