The present study was carried out in pots during two growing seasons of 1997 and 1998 to study the effect of three levels (30, 60, and 90 kg N/ fed.) of three  nitrogen sources (ammonium nitrate, calcium nitrate and urea) on growth, yield and some chemical compositions of rapeseed plants (Brassica napus L. variety N. A. 145). The obtained results indicated that, plant height, total leaf area/plant, dry weight of roots and shoots as well as number of fruiting branches/plant were significantly increased by applying different nitrogen levels. Besides, the different nitrogen sources at the level of 60 kg N/fed. significantly increased rapeseed yield and its components as well. Chlorophylls a, b and carotenoids, nitrate reductase activity, NPK contents, total carbohydrates and total free amino acids in leaves, as well as NPK concentrations, total carbohydrates, crude protein and oil percentage in seeds were also, increased by increasing nitrogen levels up to 60 kg N/fed. Meanwhile, only oil percentage and yield/plant were decreased with 90 kg N/fed. by different nitrogen forms. In this concern, the application of ammonium nitrate followed by urea at the level of 60 kg N/fed. was the most effective level among the different applied nitrogen sources and levels on seed yield and oil yield of rapeseed plants.