Rates of reactions of methanesulfonyl chloride with various substituted anilines have been measured in methanol. Substituent effects in aniline are found to be linearly correlated with pKa(Bronsted relation with ${eta}$ = 0.84) and ${ ho}$(Hammett equation with ${ ho}$ = -2.46) respectively. The results are interpreted in terms of degree of bond-formation at the transition state, which was found to have progressed relatively further. The rates for o-methylaniline deviated from the Bronsted plot established by meta and para substituted anilines because of a steric effect of ortho position in aniline. Activation parameters, ${Delta}H^{ eq}$ and ${Delta}S^{ eq}$ have also been determined. The enthalpy of activation showed a regular variation in that electron donating substituents in the p-substituted aniline decrease ${Delta}H^{ eq}$ and increase the negative value of ${Delta}S^{ eq}$