The kinetics of the transacylation reaction between different N-acylanilines and ring-substituted acetanilides with dicarboxylic acids in the molten state and in the absence of solvents have been studied. The rates of the formation of the cyclic imides were determined using g.l.c. for the analysis of reaction mixtures at various times. Ring substituents in the acetanilide were found to influence the reaction only slightly while the size of the acyl group in different N-acylanilines had a pronounced effect. Kinetic complications and the mechanism of the reaction are discussed.