Two field experiments were carried out at Agric. Res. Stat., Fac. Agric.,Cairo Univ., during 2000 and 2001 seasons to study the effect of nitrogen fertilizer levels on growth, yield and yield components of some maize cultivars under two farming systems. Data revealed that number of days to emergence, plant height, ear height, yield and its components of   no- tillage system (NT) were lower than those of conventional system (CT). Increasing N level from 80 to 110 or 140 kg / fad significantly delayed tasseling and silking. Application of 140 kg N/fad increased grain yield/ fad, over the 80 and 110 kg N/ fad by 42.76 and 10.81% in the first season and by 39.60 and 9.61% in the second season, respectively. Both single cross 10 and three-way cross 310 hybrids surpassed the open pollination cultivar Giza 2 for plant height, ear height, number of leaves / plant and ear leaf area. While, Giza 2 cultivar was the earliest in tasseling and silking. SC 10 hybrid exceeded TWC 310 hybrid and Giza 2 cultivar in grain yield /fad by 5.51 and 15.49% in the first season and 5.61 and 14.51% in the second one, respectively. SC10 produced greatest ear leaf area under the conditions of CT system and 140 kg N / fad. Under the condition of CT system SC 10 hybrid with 110 kg N/ fad or 140 kg N/ fad produced highest grain yield / fad. It could be concluded that SC10 is the best studied cultivar and could be produce greatest grain yield under the CT system with 110 kg N/ fad. However, under no- tillage system, the highest grain yield was obtained with growing SC 10 and 140 kg N / fad.