Two field experiments were conducted during 2011and2012season at Gemmeza Research Station,El Gharbia Governorate,Egypt,to study the effect of  two  winter crops(pure stands of fodder beet and Lentil in addition to their mixed cropping) on two successive summer crops of sunflower and maize. The first experiment was initiated in 2010/2011 winter season and terminated in 2011 the summer season whereas; initiation and termination of the second experiment were winter and summer seasons of 2011/2012,respectively.  The experimental design was split-plots design with three replication, where the preceding winter crops (fodder beet, mixed fodder beet +lentil and lentil) comprised the main plots (Both sunflower (Sakha 53 cv.) and maize (Giza 310 Cv.) were sown following the two winter crops as a relay crop into pure fodder beet (S₁) and mixed fodder beet and lentil (S₂) after lentils removal in addition after lentils as a double crop (S₃)) and three nitrogen levels (N₁=90, N₂=105 and N₃=120 kg N/feddan) were tried in a sub-plot. Each sub-plot was 24 m² in area, consisting of 5 ridges (each, 4 m long and 1.2 m wide).                                                                                                                                 Results were summarized as follows; 1-All the traits of sunflower were significantly affected by preceding winter crops in both seasons,except,plant height and No. of leaves/plant in  both seasons. 2-All characters of maize were significantly affected by preceding winter crops and nitrogen levels in both seasons,expect, ear leaf area in both seasons . 3-The interaction between preceding crops and nitrogen levels had insignificant effect on all traits of sunflower and maize in both seasons. 4-The highest values of Land equivalent ratio(LER)were  1.405  and  1.472  in the two seasons,respectively,with preceding crops. 5-The highest values ofArea time equivalent ratio(ATER) were  (  1.306   and  1.343)     in the two seasons,respectively, with preceding crops. 6- The highest values of Relative crowding coefficient(RCC) were(6.76       and 7.79)      in the two seasons,respectively, with preceding crops. 7-Aggressivity(Ag) indicated that  sunflower  was  the dominat crop ,whereas, maize was the dominated in both seasons. 8-The highest values of cereal units  were observed by lentil  for preceding crop. 9-The highest gross return was obtained  by lentil with(N3).