This study was carried out during 2010 and 2011 seasons on 14 years old Washington navel orange trees (C. sinensis, L.) grown on two citrus rootstocks (Volkamer lemon and Sour orange) and spaced at 5x5 m in private orchard at Kafrelshikh Governorate, to study the effect of these two rootstocks on fruit splitting under Kafrelshikh climatic conditions. The obtained results showed that, trees on Volkamer lemon rootstock gave a highest value of yield, peel thickens, and fruit and navel shape and less % of splitting when compared with those on Sour orange rootstock in both seasons. Also, the results showed a positive relationship between crop load and the percentage of fruit splitting. Fruit splitting is greatest when crop load is heavy from season to season. The results also cleared that the large number of splitted fruit was counted among a large sized of fruit. The splitting fruit recorded less value of peel thicknes when compared with healthy one for both rootstocks. Also, peel thickness at stylar end measured least values for both healthy and splitted fruit. Leaf analysis recorded the highest values of N, K, Ca and Mg concentrations and least values of P and Na on Volkamer lemon with subordinate % of splitting when compared with Sour orange rootstock, which exhibited higher values. Also,Leaf analyses in this study did not show any deficient in these nutrients. Peel analysis recorded lower values of Ca and Mg in the peel of splitted fruit when compared with those in the peel of healthy one. These inadequate values of Ca and Mg in the peel of splitted fruit may be a factor responsible for inducing splitting of Washington Navel orange fruits.