Nucleophilic substitution reactions of methylthiocyanate(MTC) with anion nucleophiles,$SH^-,;CN^-$ and $OH^-$, have been investigated using MNDO method. For the three reaction centers of MTC, gas-phase and solution-phase selectivities are discussed for each nucleophile by considering potential energy profiles calculated(intrinsic term) and magnitudes of negative charge on the nucleophile at the transition state(solvation term). It was found that both components of the selectivity for $SH^-$agreed with the experimental results obtained for 4-methylbenzylthiocyanate (4-MBTC), but the selectivity order for TEX>$CN^-$</TEX> was found to agree only with that of the intrinsic term and that of $OH^-$disagreed with any theoretical selectivity order. The MNDO optimized geometries for all species at the stationary points are reported.