Succinic acid compounds of the formula: ##STR1## wherein A represents a heterocyclic group, a 3 to 8-membered cycloalkyl group or a phenyl group which may have one or more substituents selected from the group of a halogen atom, a lower alkyl group having 1 to 6 carbon atoms and a lower alkoxy group having 1 to 6 carbon atoms; B represents a bicyclic amino group which may have 1 or 2 unsaturated bonds, with the proviso that B bonds to the carbon atom of the carbonyl group at the nitrogen atom; R represents a hydrogen atom or combines each other to form a chemical bond; R.sup.1 represents a hydrogen atom, a lower alkyl group having 1 to 6 carbon atoms or an aralkyl group having 7 to 10 carbon atoms; when there is an asymmetric carbon atom, enantiomers thereof and racemic mixtures thereof; when there are geometrical isomers, each geometrical isomer, E-isomers thereof, Z-isomers thereof, cis-isomers thereof and trans-isomers thereof; and pharmaceutically acceptable salts thereof, enhance insulin secretion and possess a hypoglycemic activity, and are thus useful for the treatment of diabetes.