Oketsu-night sweat was first mentioned in the “Yi lin gai cuo” by Wang Qing ren and the “Xue zheng lun” by? Tang Rong chuan, but there are few explanations of its disease condition. Thus we made pathological studies in Oriental medicine based on three cases (women), where Oketsu-sho was alleviated with Keppu-chikuo-to modification, and Teitou-gan and Tokaku-joki-to (Tao he cheng qi tang) modification. Common disease conditions were Netsu-sho or heat syndrome (summer incidences, redness, flushing during night sweat), and lower Oketsu symptoms (lower abdominal distention, distention and cramping of the lower abdomen, and increased urinary frequency). The theory of these disease conditions is as follows: During sleep, Wei-energy enters the blood. Because of this, Wei-energy of the body surface becomes asthenia making it easier to break out in sweat. The Wei-energy in the blood is depressed by Oketsu, and heat of Oketsu becomes stronger during the night. This fever heats and evaporates bodily fluids, and as a result fluids are pushed outward and cause night sweat. Therefore heat syndrome appears to be a pre-condition of Oketsu-night sweat. If the lower aspect of the body is taken to mean the liver, one would hypothesize that Oketsu-night sweat is more likely to emerge because blood accumulates in the lower area because it returns to the liver at night. Thus, it is thought to be necessary to consider Oketsu as one of the causes of night sweat.