The invention relates to 4-oxoimidazolidine-2-spiropiperidine derivatives represented by a general formula [I] ##STR00001## [in which A.sub.1, A.sub.2, A.sub.3, A.sub.4 and A.sub.5 stand for optionally halogen-substituted methine, or nitrogen atom; R.sup.1 and R.sup.2 stand for lower alkyl or the like; R.sup.3 stands for hydrogen or lower alkyl; R.sup.4 and R.sup.5 stand for hydrogen, or lower alkyl which is optionally substituted with hydroxy, or the like]or salts thereof. These compounds act as nociceptin receptor agonist, and are useful as analgesic, reliever from tolerance to narcotic analgesic, reliever from dependence on narcotic analgesic, analgesic enhancer, antiobestic, drug for ameliorating brain function, remedy for schizophrenia, drug for treating regressive neurodegenerative diseases, antianxiety agent or antidepressant and remedy for diabetes insipidus and polyuria; and the like.