Corn starch of different physical forms (solid and liquid) was irradiated with 60Co gamma rays and electron beam in the dose range of 50 Gy to 100 kGy to investigate the effect of ionizing radiation on its molecular weight (Mw). Degradation was observed for both solid and liquid states upon radiation. However, degradation of the starch in the liquid state was remarkably greater than that in the solid state. The free radicals that formed during water irradiation must be responsible for such degradation in the liquid form. Thermostated viscometer, rheometer and multiangle static laser light scattering were employed to study the changes in the Mw of corn starch that occurred during irradiation at constant temperature and different concentrations. It was observed that electron beam irradiated corn starch has uniform decreasing in Mw and radius of gyration (Rg) in the range of (4.4×1072.9×107 g mol?1) and (199.385.6 nm), respectively. The influence of gas atmosphere on the degradation process during gamma irradiation was studied to find that, the Mw and Rg values were in the range of (4.4×1071.8×107 g mol?1) and (199.3120.4 nm) for the oxygen saturated samples, while, they were (4.4×1071.05×107 g mol?1) and (199.385.6 nm) for the argon saturated samples.