The influence of 6-aminocaproic acid on the polymerization of caprolactam has been studied. Samples of five sets of different mole ratios of the catalyst and caprolactam were sealed in separate tubes and heated at 230±1° in a specially designed tube furnace. They were taken out at various time intervals and analyzed for the contents of monomer cyclic oligomer and high polymer. The average molecular weights of the polymer were also determined.