The reactivity of amino groups attached to N-N′-methylene-bis-acrylamide (NNMBA)-and triethyleneglycol dimethacrylate (TEGDMA)-crosslinked polyacrylamide gels (2–20 mol% crosslinked) has been investigated by following the aminolysis ofp-nitrophenyl ester of benzoyl glycine in a mixed solvent. A differential method was employed for following the rate of aminolysis reaction at definite intervals of time. The extent of aminolysis was found to be maximum between 25 and 35 min after initiation for these resins. The rate constants were calculated using the equation for three-dimensional phase boundary model with spherical symmetry and three-dimensional diffusion model. The reaction appears to be a phase boundary process up to 40 min after initiation and thereafter is fully controlled by three-dimensional diffusion. The rate constants do not show any dispersion when this model is used.