Water quality of sub- and deltaic regions of the River Nile in Egypt was seasonally investigated from autumn, 1987 to summer, 1988. Sixteen different sampling stations, distributed along the River Nile, its two main branches and some canals, were selected to cover the study area. The physical and chemical properties of water displayed great seasonal and local variations. The parameters investigated and their ranges were, transparency (0.1-2.5 m), water temperature (12-32-degrees-C), air temperature (8-35-degrees-C), conductivity (150-1300 muS cm-1), suspended solids (6-31.5 mg dry wt l-1), turbidity (3.2-10.8 FTU), colour (7.7-10.2 mg PT l-1), sulphate (24-42 mg l-1), dissolved reactive phosphorus (0.0031. 08 mg l-1), total dissolved phosphorus (0.003-1.12 mg l-1), nitrate-N (0.035-0.823 mg l-1), nitrite-N (0.0-0.25 mg l-1), ammonium-N (0.1-3.2 mg l-1), total Kjeldahl-N (0.84-6.81 mg l-1), reactive silica (0.95-48.6 mg l-1), pH (5.8-9.01), dissolved oxygen (4-15 mg l-1), % saturation of dissolved oxygen (49-150%), biological oxygen demand (3.7-50.2 mg l-1), phenolphthalein alkalinity (0.0-23.2 mg CaCO3 l-1), carbonate alkalinity (0.0-126 mg CaCO3 l-1), bicarbonate alkalinity (2.53-235 mg CaCO3 l-1), total alkalinity (108-238 mg CaCO3 l-1), free CO2 (0.65-430 mg l-1), total CO2 (86-628 mg l-1), total hardness (68-237 mg CaCO3 l-1), chlorides (7.6-59.9 mg l-1), Ca (26.8-49.8 mg l-1), Mg (11.3-18.2 mg l-1), Na (11.2-70.4 mg l-1), K (1.83-8.2 mg l-1), Al (48-162 mug l-1), Cd (<1.0-2.4 mug l-1), Cu (5-97 mug l-1), Fe (26-654 mug l-1), Pb (<1.0-15.1 mug l-1), and Zn (7.8-18.1 mug l-1). Inferior water quality conditions were observed at the downstream sampling stations. Pollution point sources (industrial effluents) exerted negative local effects on water quality of the receiving waters. The multivariate analysis divided the sampling stations in 3 distinct groups. One comprising the upstream sites, another consisted mainly of sites distributed along canals, and the third including downstream stations located lengthwise Damietta and Rosetta branches of the River Nile. The multiple correlation analysis revealed the pattern of interrelationships between physical and chemical parameters. For instance BOD5 showed a highly significant (p<0.001) positive correlation with dissolved reactive phosphorus (r=0.73), and a negative one with the pH (r=-0.73). Compared to water quality standards of European Communities Directives and U. S. Environmental Protection Agency, waters of the area studied mostly sustained a tolerable chemical water quality for domestic uses.