The sin-let and triplet potential energy surfaces (PESs) of boron-carbon-phosphorus(BCP) isomers were investigated, using various theoretical methods. Geometries of the minima and transition states on the PES were optimized at the B3LYP/6-311+G(2df) and CASSCF(12,12)/6-311+G(2df) levels, and single-point calculations were made at the CASPT2/ANO-L level, to consider dynamic electron correlation effects. The most-stable isomer was linear singlet BCP (111); its calculated heat of formation (Delta(f)Hdegrees, 0 K) is 150.5 +/- 2 kcal/mol. Study of the fragmentation processes in BCP revealed that the bond enthalpies of the B-C and C-P bonds in BCP ((1)Sigma(+)) at 0 K are 111.7 and 128.9 kcal/mol, respectively, at the CASPT2/ANO-L level. A possible crossing mechanism between two electronic states ((3)A' and (3)A") is discussed, and Renner-Teller species with (3)Pi state symmetry are investigated.