Two field trials in a split plot design with four replications were carried out at Sakha Research Station (Kafr El-Sheikh Govemorate) during 2001/2002 and 2002/2003 seasons to study the influence of potassium and magnesium fertilization on yield and quality of two sugar beet varieties. Each experiment consisted of 18-treatments repesent two varieties (Pleno and Toro), and three potassium sulfate (48% K₂0) levels zero, 24 and 48 kg K₂0/fed and three magnesium sulfate (24% Mg0) levels zero, 5 and 10 kg MgO/fed. Varieties were assigned in main plots whereas the combinations betewen fertilizer treatments were destributed in subplot The results showed that sugar beet variety Toro significantly surpassed variety Pleno in root diameter, root fresh weight, top and root yields (tons/fed) in the 2n^d one. Potassium fertilizer attained a significant difference in root length, root diameter, root fresh weight, sucrose%, purity% and top yield (tons/fed) in both seasons. Morover, magnesium fertilizer produed a significant effect on root length, diameter, root fresh weight, top and root yield in the 1¹ season. The highest values of root (45.54 tons/fed) and sugar (8.34 tons/fed) yields resulted from the interaction between Toro variety, fertilized by 5 kg MgO/fed and 24 kg K₂0/fed in the 1^st season and (43.55 tons roots/fed) and (7.9 tons sugar/fed) resulted from the interaction between Toro variety, fertilized with 5 kg MgO/fed and 48 kg K20/fed in the 2^m1 season., respectively.