The present investigation was carried out in the Exper imental Farm, Faculty of Agriculture at Noshtohor, Zagazig University during 1990 and 1991 seasons to study the response of cotton to N, P levels and time of nitrogen application as well as their interaction. The treatments were designed split plot with four replications. The results could be summarized as follows: Seed cotton yield per fed— dan, yield components and fiber properties were not signifi cantly affected by phosphours levels in combined analysis. Plant height and number of unopened boils/plant were significantly increased by increasing N level up to 90 kg per f eddari. Number of plants per feddan at harvest and lint percentage were decreased by increasing N levels. Applying 30 kg N/fed. gave the highest seed cotton yield per feddan, lint yield/feddan as well as fiber 1ength. Seed index was significantly increased by increasing N levels in both seasons, whereas number of sympodia per plant, number of open bolls / plant, boll weight, seed cotton yield / plant and fiber properties were not significantly affected by N levels. The best time of N fertilizer application was obtained by applying 1/2 N after thinning + 1/2 N dose before the second irrigation. On the other hand, yield components and fiber properties were not significantly affected by applica tion time. The interaction between phosphorus and nitrogen levels affected significantly number of open boils / plant, boll weight, seed cotton yield / fed. and lint yield / feddan. Seed cotton yield / fed. and lint yield / fed were signifi cantly affected by the interaction between N levels and * This study is a part of the project NARP ،!oshtohor No, 247 (Econ. Agric., and Ext. Dept. Fac Agric. Moshtohor).