Two field experiments were conducted at Sakha Agriculture Research Station during 1997 and 1998 seasons using the Egyptian cotton cultivar Giza 87 (Gossypium barbadense L.). The aim of this investigation was to study the effect of irrigation intervals and plant population density on growth, earliness and seed cotton yield and its components. A split plot design with four replications was used. The main plots were assigned to irrigation intervals (every two weeks, every three weeks and every four weeks). Each sub-plot consisted of six ridges, 5 m in length and 60 cm. apart were allocated to the three plant population densities i.e., 70000, 56000 and 46666 plants/fed.                 The combined data clarified that irrigation interval every two weeks increased final plant height, number of main stem internodes, both sympodial and monopodial branches, total dry weight, number of open and unopen bolls, boll weight, lint % and seed cotton yield (kintar/fed., while it decreased main stem internodal length and percentage of plant losses. Also, the same treatment induced delay in maturation as it increased number of days to both first open flower and boll as well as  decreased earliness percentage irrespective to higher values of boll set and fewer shedding percentage. Node location of the first sympodium and seed index did not affect by irrigation intervals. On the other hand, increasing plant population density from 46,666 up to 70,000 plants/fed., generally increased final plant height main stem internodal length, number of unopen bolls; percentage of plant losses and seed cotton yield (kintar/fed.), while it decreased number of main stem internodes, both sympodial and monopodial branches, total dry weight and number of open bolls. Although higher plant density (70,000 plant/fed.) raised node location of first sympodium and increased shedding percentage associated with lower boll set, it enhanced maturation by reducing number of days to both first open flower and boll as well as increasing earliness percentage. Plant population density failed to exert any significant effect on boll weight, lint % and seed index. The interaction between irrigation intervals and plant population density did not affect all characters studied herein.                 Seasonal consumptive use in cubic meters per feddan and water use efficiency were decreased as either irrigation intervals increased or plant population density decreased in both seasons.