The effect of oxidant levels on the structure and physico-chemical properties of modified cassava starch was investigated. Cassava starch was treated with various amounts of sodium hypochlorite (1,000- 20,000 ppm of active chlorine on dry starch basis) at 30°C and pH 10.5. The substantial amount of carboxyl groups was formed only when more than 5,000 ppm of hypochlorite was used and it increased with increasing hypochorite levels. With these high levels of hypochlorite, the resulting modified starches exhibited the pasting properties of a typical oxidized starch with low peak viscosity, little breakdown and low setback. With the lower levels of hypochlorite (1,000 and 2,500 ppm), the modified starches showed high peak viscosity, reduced breakdown and high setback. Results from high-performance size-exclusion chromatography reveals that both amylose and amylopectin were degraded and the extent of degradation increase with the increasing levels of the oxidant. Starch modified with hypochlorite concentration lower than 2,500 ppm showed a pronounced reduction in the paste clarity indicating that the starch granule becomes more resistant to disintegration after the modification.