Two new less-symmetric P(OH)(3) isomers that are more stable than the C-3 structure are found at the density functional theory (B3PW91, B3LYP), MP2, and CCSD(T) levels with the large aug-cc-pvdz/pvtz basis sets. The C-1 and C-3 structures are qualitatively different from those found for the As(OH)(3) molecule. An additional lower lying P(OH)(3) structure with C-s symmetry has been obtained. With the largest basis set the C-s isomer is predicted to be the most stable. However, the inclusion of zero-point-energy corrections induces an inversion between the C-s and C-1 isomers, with the latter becoming the lowest energy structure at the highest correlated level. Increasing inclusion of electronic correlation effects reduces the energy difference between the C-1 and C-s structures while the C-1-C-3 energy difference and C-1-C-s interconversion barrier become larger. In all cases, energy differences and barrier heights are around 1 kcal/mol.