In order to study the effect of interstock length of mango cv. Nam Dok Mai, a twelve - month trial was intitiated. The interstock lengths were 7.5 , 15.0, and 22.5 centimeters grafted on `Kaew rootstocks. Scions were consisted of `Nam Dok Mai , `Khiew Sawoey and `Raad. Growth measurement of those grafted scions was recorded, when the graft union completely established, after four months. The results showed that interstock influnce on scion growth, length, and diameter were not significantly difference at any particular length. Whereas trees with 7.5 cm interstock obtained the larger interstock diameter. On the other hand degrees of congeniality, between scion and interstock, were depending on the length of the time after formation of the graft union Development of graft union was less congenial in the 7 months than those 12 months. In case of leaf nutrient content, the total non-structural carbohydrates (TNC) , total nitrogen (TN), phosphorus (P), potassium (K) and calcium (Ca) showed no significant difference statistically with interstocks. These effects were found in both periods, 7 and 12 months, after union formation. However, TNC decreased in 12th month in contrast to the increasing of Ca content. The changes of these nutritional contents were largely caused by age or stage of leaf growth. No insertion of interstock indluence found in this experiment.