The structure, infrared spectrum, and heat of formation of B2N, B2N-, BO, and B20 have been studied ab initio. B2N is very stable; B20 even more so. BIN, B,N-, B20, and probably B2N+ have symmetric linear ground-state structures; for B20, an asymmetric linear structure lies about 12 kcal/mol above the ground state. B,N+, B2N-and B20 have intense asymmetric stretching frequencies, predicted near 870, 1590 and 1400 cm-', respectively. Our predicted harmonic frequencies and isotopic shifts for B20 confirm the recent experimental identification by Andrews and Burl&older. Absorptions at 1889.5 and 1998.5 cm-' in noble-gas trapped boron nitride vapor belong the BNB and BNBN (?I), respectively; a tentative assignment of 882.5 cm-' to BNB+ is proposed. Total atomization energies 1 D, (1 Do) are computed (accuracy ? 2 kcal/mol) as: BO 193.1 (190.4), BzO 292.5 (288.7), B2N 225.0 (250.3) kcal/mol. The ionization potential and electron affinity of B2N are predicted to be 8.62 fO.l and 3.34 +O. 1 eV. The MPClevel additivity approximations involved in Gl theory results in errors on the order of 1 kcal/mol in the 1 D, values.