The following points derived from a kinetic study of the Knorr-Paal condensation prove that its mechanism can be no other than a simple carbonyl addition and eliminative dehydration: (1) It has the most striking feature of a characteristic bell-shaped graph of reaction rate as a function of pH. (2) It has unusually large negative activation entropy as well as extremely low activation enthalpy. (3) For the conden-sation of ρ-qrethogyaniline and β-diketone with ρ-substituted benzoic acids as catalysts, it also has the characteristic Brönsted α value 0.25. (4) It has a Hammett plot of ρ⁺=-0.881 which also correlates with the rates mnch better than ρ^- or ρ. (5) These condensations have excellent LFR with those of acetylacetone with the same group of anilines.