Guh Sung Y.L.S.-95 is one of the polyacidic solution of which main component is acetic acid. We investigated the subchronic toxicity of the Guh Sung Y.L.S.-95 using SPF ICR mouse for 4 weeks. The Guh Sung Y.L.S.-95 was administered by gastric intubation, 1.0, 2.5, 5.0 g/kg body weight. The results are as follows: 1. There are no adverse effects on the clinical obserbation and body weight changes. Also, there are some significant changes in organ weight, but it was meaningless because of the absence of dose-response relationships. 2. In the hematological patterns of administered mouse, there are no significant changes between the treated groups. Also, there are no serological enzymatic changes in the treated mouse. In the 1.0 g/kg treated group, ASP activity was increased significnatly compared with control group. But, this level of activity was fall under the normal physiological range of control mouse. 3. Histopathological findings of the brain, liver, heart, spleen, kidneys, stomach, lung, testis, ovary, uterus and thymus were not observed in the treated mouse. From the above results, the Guh Sung Y.L.S.-95 has no toxicity upto the 5.0 g/kg/day of oral dose for 4 weeks.