Thermochemical data of boron subphosphide are derived from reported decomposition data of cubic boron monophosphide BP. Both reported boron subphosphides, i.e. B6P and B13P2, are taken into account, without claiming either of these to have the reported stoichiometry. The standard heat of formation Delta(f)H(0), the standard entropy S-0, and the heat capacity as a function of temperature C-P,T(0), pf B6P and B13P2 are Delta(f)H(0) = 69.2 -/+ 11.4 kJ/mol, S-0 = 213 -/+ 15 J/mol K, and C-P,T(0) = (42.0 -/+ 0.9) + (0.166 -/+ 0.004) x TJ/mol K, and Delta(f)H(0) = 175 -/+ 4 kJ/mol, S-0 = 462 -/+ 10 J/mol K, and C-P,T(0), = (87.6 -/+ 1.8) + (0.359 -/+ 0.008) x TJ/mol K, respectively.