Hypoglycemic thiazolidine-2,4-dione derivatives of formula (I), wherein the dotted line represents a bond or no bond; V is -CH=CH-, -N=CH-, -CH=N-, S, O or NR; W is S, SO, SO2, SO2NR1, NR1SO2, CONR1 or NR1CO; X is S, O, NR2, -CH=N- OR -N=CH; Y is CH or N; Z is hydrogen, (C1-C7)alkyl, (C3-C7)cycloalkyl, phenyl, pyridyl, furyl, thienyl or phenyl mono- or disubstituted with the same or different groups which are (C1-C3)alkyl, trifluoromethyl, (C1-C3)alkoxy, fluoro, chloro or bromo; Z1 is hydrogen or (C1-C3)alkyl; R, R1 and R2 are each independently hydrogen or (C1-C4); and n is 1, 2 or 3; a pharmaceutically acceptable cationic salt thereof; or a pharmaceutically acceptable acid addition salt thereof when the compound contains a basic nitrogen.