The purpose of this study was to evaluate the cleansing effect of Glyoxide on the dentinal walls of the root canal. Fourty teeth were divided into four groups and the canals in each group were individually enlarged with K-file by step-back technic and irrigated with one of four irrigants. The four used irrigants were Glyoxide (Marion lab. U.S.A.) in combination with 3.5% sodium hypochlorite, 3.5% sodium hypochlorite, 3.5% sodium hypochlorite in combination with 3% hydrogen peroxide and normal saline solution. All the irrigants were used in conjunction with instrumentation as they would be during clinical conditions. After final irrigation, the canals were dried with paper points and the teeth were split longitudinally. The cleaness of canal walls according to the size and the level of canals were evaluated under steroscope by t analysed statistically The results were as follows. 1. The use of 3.5% sodium hyphochlorite in combination with 3.0% hydrogen peroxide revealed the most clean canal surface regardless of the size of canal at apical third of root canal (p < 0.05). 2. Glyoxide in combination with 3.5% sodium hyphchlorite showed no significant difference in cleaning effect of canal surface compared with 3.5% sodium hypochlorite and normal saline solution at the apical third of narrow canal. 3. Glyoxide in combination with 3.5% sodium hypochlorite revealed no significant difference in debridement of canal walls compared with 3.5% sodium hypochlorite in combination with 3% hydrogen peroxide and saline solution at the middle third of narrow and large canals.