Two field experiments were carried out during 1980 and 1981 seasons at the Research and Experimental Station of the Fac, of Agric., Moshtohor, Zagazi Univ., to study the effect of three nitrogen levels (0, 45 and 90 kg N/fed.) and the three chemical defoliants (Dropp 40, 80 and 120 g/fed.; Harvade 124, 250 and 375 cm./fed. and Gramoxon 100, 200 and 300 cm./fed..) on cotton Giza 69 and 75. Results showed that increasing nitrogen level up to 45 kg. N/fad. resulted in increasing significantly the number of green leaves/plant, plant height, number of open bolis/plant, boll weight, seed cotton yield/plant and per fed, and protein percentage in the seeds. Percentage of defoliated leaves was signifiacntly increasaed by the applied defoliants as compared with the undefoliated plants in both seasons except, the 100 cm. Gramoxon. Defoliants showed signifianCt effect on boll weight and seed cotton yield/fed. in one season and on oil percentage of the seeds in both seasons. The effect of the interaction between N-levels and defoliantS was significant on seed cotton yield/plant, protein and oil percentage of the seeds in 1980 season and percentage of defoliated leaves, number of open boils/plant, seed cotton yield/fed. and oil percentage in 1981 season.