Ten olive (Olea europea, L) orchards at Siwa Oasis were selected to study the effect of well water quality on yield, oil content, fruit properties, leaf characteristics and soil chemical analysis during 1998 and 1999 growing seasons. Irrigation water for every orchard was taken from one well drilled in it. Two olive cultivars (Hamid and Wetteken) were used in this study. The data for both seasons, generally revealed that, increasing water salinity (EC_iw) markedly decreased yield, oil content and fruit weight, volume, length and diameter, for both cultivars. Moreover, seed weight, length and diameter significantly decreased with increasing EC_iw. With regard to flesh characteristics flesh weight, thickness and percent  behaved similar trend. The data also revealed that the reduction of Wetteken cv. yield was more pronounced as compared with Hamid cv. Meanwhile oil content gave an adverse trend. Leaf area, leaf total chlorophyll and water contents significantly decreased as a result of increasing water salt content. Leaf, N, P, K, Fe, Mn, Zn, Cu and B contents decreased, while Ca, Mg, Na and Cl increased with increasing EC_iw for both cultivars. High salt content of irrigation water significantly increased pH, EC, soluble cations , anions and soil nutrient contents.