A melanin-concentrating hormone antagonist which comprises a compound of the formula: ##STR00001## wherein Ar.sup.1 is a cyclic group which may have substituents; X is a spacer having a main chain of 1 to 6 atoms; Y is a bond or a spacer having a main chain of 1 to 6 atoms; Ar is a monocyclic aromatic ring which may be condensed with a 4 to 8 membered non-aromatic ring, and may have further substituents; R.sup.1 and R.sup.2 are independently hydrogen atom or a hydrocarbon group which may have substituents; R.sup.1 and R.sup.2, together with the adjacent nitrogen atom, may form a nitrogen-containing hetero ring which may have substituents; R.sup.2 may form a spiro ring together with Ar; or R.sup.2, together with the adjacent nitrogen atom and Y, may form a nitrogen-containing hetero ring which may have substituents; or a salt thereof; which is useful as an agent for preventing or treating obesity, etc.