Heterocyclic dihydroxyquinoxaline compounds having the formula ##STR1## wherein R.sup.1 is hydroxy; andR.sup.5 and R.sup.6 together form a fused phenyl, cyclohexyl or pyridyl ring, which is optionally substituted with halogen or CN; and R.sup.7 and R.sup.8 independently are hydrogen, hydroxy, NO.sub.2, halogen, CN, CF.sub.3, C.sub.1-4 -alkoxy, acetyl, SO.sub.2 NHCOCO.sub.2 Et, SO.sub.2 NR'R' or SO.sub.2 R', wherein R' is hydrogen or C.sub.1-4 -alkyl; orR.sup.5 and R.sup.6 independently are hydroxy, hydrogen, NO.sub.2, halogen, CN, CF.sub.3, C.sub.1-4 -alkoxy, acetyl, SO.sub.2 NHCOCO.sub.2 Et, SO.sub.2 NR'R' or SO.sub.2 R', wherein R' is hydrogen or C.sub.1-4 -alkyl; and R.sup.7 and R.sup.8 together form a fused phenyl, cyclohexyl or pyridyl ring which is optionally substituted with halogen or CN.The invention also relates to a method of preparing the compounds, pharmaceutical compositions thereof, and their use.The compounds are useful in the treatment of indications caused by hyperactivity of the excitatory neurotransmitters, particularly the quisqualate receptors, and especially as neuroleptics.