Treatment of nylon-6 with supercritical toluene in the presence of small amounts of water resulted in an effective conversion of polyamide to give epsilon-caprolactam in quantitative yield. The presence of a small amount of water is critical for the progress of the reaction; completely anhydrous conditions failed to achieve depolymerization. epsilon-Caprolactam was readily isolated after the removal of toluene under reduced pressure. The present method can serve as a useful treatment for the effective chemical recycling of waste plastics. The combined use of hydrocarbon and water is a new technique to control the reactivity of high-temperature water.