Values of the molecular electrostatic potential minimum (V-min) corresponding to the lone pair region of several substituted phosphine ligands (PR3) have been determined at the DFT level, The V-min value is proposed as a quantitative measure of the electronic effect of the PR3 ligands. Good linear correlation between V-min and Tolman electronic parameter of PR3 has been obtained. V-min is also proportional to the pK(a) values of the conjugate acids of PR3, Viz., [PR3H](+), Further, the DeltaE values of the reaction Ni(CO)(3) + PR3 --> Ni(CO)(3)PR3 and ScH3 + PR3 --> ScH3PR3 are also linearly proportional to the V-min values. However, if there is a strong metal to phosphorus pi-back-bonding, the DeltaE and V-min do not fit to a line. It is also found that the standard reduction potential as well as the enthalpy change corresponding to the electrochemical couple eta-Cp(CO)(PR3)(COMe)Fe+/eta-Cp(CO)(PR3)(COMe)Fe-0 is linearly proportional to the V-min values of PR3. These correlations suggest that V-min is a quantitative measure of the sigma-donating ability of the phosphine. It is hoped that, in phosphine-metal coordination chemistry, the V-min based electronic parameter could be more advantageous than nu-CO and pK(a) based electronic parameters as it solely represents the inherent electronic property of the ligand.