A series of novel spiro-oxindole imidazolidinedione derivatives have been prepared, including their pharmaceutically acceptable salts. These compounds are useful in therapy as aldose reductose inhibitors for the control of certain chronic diabetic complications. Preferred compounds include 6'-amino-spiro-[imidazolidine-4,3'-indoline]-2,2',5-trione, 5'-chloro-7'-amino-spiro-[imidazolidine-4,3'-indoline]-2,2',5-trione, 1'-(3-pyridylmethyl)-5'-fluoro-spiro-[imidazolidine-4,3'-indoline]-2,2',5-trione, 1'-(3-pyridylmethyl)-5',7'-dichloro-spiro-[imidazolidine-4,3'-indoline]-2,2',5-trione and spiro-[imidazolidine-4,3'-(6-azaindoline)]-2,2',5-trione. Methods for preparing these compounds from known starting materials are provided.