Department of Chemistry, Shivaji University, Kolhapur-4 Manuscript received 15 March 1971; accepted for publication 9 January 1972 Kinetics of acid hydrolysis of propionamide has been investigated in 0.05 to 7 M perchloric acid at 70°. The rate constants increase with an increase in acid concentration and attains optimum value in 3 M acid. Arrhenius parameters, kinetic order and the ionic strength data support a bimolecular nucleophilic attack of water on the conjugate acid species of propionamide. The variation of reaction rate with acid concentration is explained in terms of a two parameter equation which takes into account the relative amounts of free and protonated substrate and a kinetic salt effect and the water activity raised to some power.