A G1 and G2 study of the triplet [H-4, C, O, P](+) potential energy surface (PES) has been carried out, along with a study of a number of mechanisms for the reaction of the P+ ((3)p) ion with methanol. The most stable isomer, which corresponds to the insertion of the phosphorus cation into the C-O bond of methanol, lies 79.5 kcal/mol below the reactant level. The P+-H3COH ion molecule complex has also a remarkable stability, -72.0 kcal/mol, showing that methanol exhibits greater basicity than water or formaldehyde. Bond properties have also been evaluated for all the minima encountered on the PES. Several barrier-free reaction paths have been characterized. The most exothermic channel involves abstraction of H-2, although this path is kinetically disfavored. In this sense, the most favored reaction leads to the formation of the doublet POH+ ion with the release of doublet CH3, in agreement with experimental evidence. However, other barrier-free channels were also found, pointing to a variety of possible products for the P+ + H3COH reaction.