A series of novel 3-mono(substituted methyl)- and 3,3-di(substituted methyl)-2-oxo-indoline-1-alkanoic acid compounds have been prepared, including their lower alkyl esters and unsubstituted amide derivatives, as well as the base salts of said acids with pharmacologically acceptable cations. These compounds are useful in therapy as aldose reductase inhibitors for the control of certain chronic diabetic complications. Said oxindole-1-alkanoic acid compounds are of the formulae: ##STR1## wherein X is hydrogen and X.sup.1 is hydrogen, hydroxy, fluorine, chlorine, bromine, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; or X and X.sup.1, when taken separately, are each chlorine, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy, and when taken together are --OCH.sub.2 (CH.sub.2).sub.n O-- at the 4,5-, 5,6- or 6,7-positions of the molecule wherein n is zero or one; R.sub.1 is hydrogen or methyl; R.sub.2 is hydrogen, C.sub.1 -C.sub.4 alkyl or phenylalkyl having up to three carbon atoms in the alkyl moiety wherein said phenylalkyl is optionally substituted with up to two chlorine substituents on the phenyl ring; R.sub.3 is naphthylmethyl, furfuryl, thenyl, benzothienylmethyl, benzoxazolylmethyl, benzothiazolylmethyl or phenylalkyl having up to three carbon atoms in the alkyl moiety wherein said phenylalkyl is optionally substituted with up to two identical or non-identical substituents on the phenyl ring, said identical substituents being fluorine, chlorine, bromine, trifluoromethyl, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy and said non-identical substituents being chlorine, methyl, methoxy or trifluoromethyl; and Y is hydrogen, fluorine, chlorine, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 -alkoxy.