Investigation on the major ions of seawater; Na + , K + , Ca ++ , Mg ++ , SO 4 À and Br À is based on more than 660 samples collected at 21 sections distributed along the Egyptian Mediterranean coast starting from Salloum to Arish during summer (2008), in addition to some samples taken at certain sections during spring (2008) and the winters of 2008, 2009 and 2010. In respect of the analysed major ions, the total average content (mg/l) and their corresponding chlorinity ratios are as follows: Na + ; 12,337, 0.586, K + ; 381.2, 0.0180, Ca ++ ; 403, 0.0183, Mg ++ ; 1506.6, 0.0709, SO 4 À ; 3068, 0.139 and Br À ; 64.9, 0.00296. The ion content and their chlorinity ratios indicate interesting temporal and spatial fluctuations. The Mg/Ca ratio average fluctuated between 3.1 and 4.6. With respect to the total average of ion/chlorinity ratios, Na and Mg showed almost positive declinations above the normal oceanic ratios. K, Ca and Br/chlorinity ratios, on the other hand, deviated strongly below normal while SO 4 /Cl ratio mean is closely nearer to normal. Strong anomalies of chlorinity ratios could be detected at several locations that coincided with high dilution and drop of salinity affected with land based effluents; e.g. in front of Mex, Krir and Sahl El-Tina areas. ª 2015 Hosting by Elsevier B.V. on behalf of National Institute of Oceanography and Fisheries. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).