In the first half of the Ming period there was a practice concerning the water control in the Chiangnan Delta, which I have conceptualized as the "t'ient'ou-chih 田頭制" elsewhere. The practice was based on the existence of managerial landlords who were resident in rural areas, i.e. "hsiangchutichu 郷居地主". In this article the author, first, indicates some new source materials, pointing out that creeks were sometimes owned by those landlords legally, that there had existed the practice of t'ient'ou-chih in the Sung period, and that those landlords had taken responsibility for collective pumping for drainage (tap'engch'e 大輣車). From the middle of the sixteenth century and on, those managerial landlords began to go bankrupt because of the development of the monetary economy and the evolution of simple commodity production in this region. The t'ientou-chih broke down rapidly, and, therefore, new practices had to be set up by the local authorities such as county magistrates, prefects and Grand Coordinators. The most typical reform was carried out by Keng Chu 耿橘, the Magistrate of C'hangshu 常熟 County at the beginning of the seventeenth century. His new regulations for water control consisted mainly of three practices, namely, "chaot'ienp'aii 照田派役", restriction of "yumien 優免"and "yehshih tienli 業食佃力". The yehshih tienli meant that the tenants should provide actual labor on behalf of gentry landlords who were mostly residing in the cities, and that the landlords should compensate the tenants for their services. Magistrate Keng prescribed that the landlords should supply tenants with rice or silver directly, but later it became a general tendency that tenants deducted the compensation from the rent due to their landlords. The term "yehshih tienli" also existed in the Sung period, and some scholars claim that the practice in the late Ming is a continuation of the one in the Sung period. But the author has a different view. This term does not appear in source materials written before the early sixteenth century in the Ming period. And this new practice, together with the other two practices, was meant to counteract the resistance of gentry landlords. The reformers such as Keng Chu made strenuous efforts to put the new regulations into practice. There are two features which distinguish the yehshih tienli of the Ming period from that of the Sung period, i.e. : i) The practice was introduced by local offcials for the relaxation of class antagonism and for the security of water control works, so it had the character of corvee labor which was levied by the Government. ii) It was against the evolution of simple commodity production infiltrating down to the handicraft produced by tenants that the new practice had to be introduced. The water control works such as the dredging of creeks, the repairing of dikes and the collective pumping for drainage encroached upon the tenants' precious time spent for handicraft work, which was indispensable for the maintenance of their families. This loss had to be made up for. These features, especially the second one, were the major differences between the practice in the late Ming and that in the Sung period.