The crude Silybum marianum oil was used for frying of potato fillets (French fries) for 4 consecutive days at a rate of 20 minutes per day. The quality constants such as peroxide value (POY), anisidme value (AY), iodine value (IY), free fatty acid (FFA) and color index as optical density (O.D at 420 nm) have been determined before and after frying. The results showed an increasmg pattern in the values of the above quality parameters. The peroxide value mcreased from 5.03 to 19.41 meql kg, AV from 1.34 to 16.4, FFA from 0.09 to 2.41 %, and color from 0.02 to 1.9. Fried Silybum marianum oil was mixed separately wlth 3 levels of MgO (4,6, g % wI w) and acttvated charcoal (2, 6, 10 % wI w). For all the treatments, the average percent improvement of quality mdices was statistically analyzed. Increasing levels of both activated carbon and MgO significantly affected (P < 0.05) the different quality parameters tested so far