Abstract: A series of spiro-hydantoin compounds has been prepared by condensing the appropriate carbonyl ring compound, such as the corresponding 1-indanone, 1-tetralone, 4-chromanone, thiochroman-4-one, 7,8-dihydroquinolin-5(6H)-one, 6,7-dihydropyridin-5(5H)-one, thiondane-3-one-1,1-dioxide and 4-oxoisothiochroman-2,2-dioxide, respectively, with potassium cyanide and ammonium carbonate. The resulting hydantoin derivatives are found to be useful in preventing or alleviating chronic diabetic complications. Preferred member compounds include spiro-[imidazolidine-4,1'-indan]-2,5-dione, 6-fluoro-spiro-[chroman-4,4'-imidazolidine]-2',5'-dione, 6-chloro-spiro-[chroman-4,4'-imidazolidine]-2',5-dione, 6,7-dichloro-spiro-[chroman-4,4'-imidazolidine]-2',5'-dione, 6,8-dichloro-spiro-[chroman-4,4'-imidazolidine]-2',5'-dione, 6'-fluoro-spiro-[imidazolidine-4,4'-thiochroman]-2,5-dione and 6',7'-dichloro-spiro-[imidazolidine-4,4'-thiochroman]-2,5-dione.