Energies and entropies of activation for the hydrolysis in dilute acid of six aliphatic amides are reported. These results, in conjunction with those of other workers, indicate the dilute acid hydrolysis of primary aliphatic amides to be governed by a combination of steric and hyperconjugative substituent effects and to be independent of polar effects. The reaction series is well correlated by the Taft-type equation �������������� logk = 0.858 EC/S-0.493(n-3)+logk0 in which EC/S denotes a pure steric substituent parameter and n is the number of α-hydrogens in the substituent. The alkaline hydrolysis of a similar series of amides is well correlated by the equation ������������ log k = 2.05�*+ 1.08 EC/S -O.743(n-3)+ log ko.