The alkylation of indol-2(3H)-one (oxindole) and of some of its mono and dialkyl derivatives has been investigated.Chromatographic methods for preparative separation and quantitative determination of the five compounds formed in the reaction between oxindole and benzyl chloride in the presence of a base are reported.A kinetic approach to these reactions shows that in unsubstituted indol-2(3H)-one the 3-position is twice as reactive as the 1-position. In the already 3-monosubstituted compound the reactivity of the 3-position is about 30 times greater than that of the 1-position.