The overall second-order rate constants of aminolysis of N-benzoyllactams of different ring size, the rate constants of aminolysis of N,N'-isophthaloyl- and N,N'-terephthaloylbis(6-hexanelactam) to the first and second stages and the ratio of splitting of the exocyclic and endocyclic amide bond by octylamine were determined in THF at 50 °C. The effect of the type of amine and medium on the rate of aminolysis was examined.