A melanin-concentrating hormone antagonist comprising a compound of the formula (I): ##STR1##

wherein Ar¹ is a cyclic group which may be substituted; X and Y are the same or different and are a spacer having a main chain of 1 to 6 atoms; Ar is a condensed polycyclic aromatic ring which may be substituted; R¹ and R² are the same or different and are hydrogen atom or a hydrocarbon group which may be substituted; or R¹ and R², together with the adjacent nitrogen atom, may form a nitrogen-containing heterocyclic ring which may be substituted; or R², together with the adjacent nitrogen atom and Y, may form a nitrogen-containing heterocyclic ring which may be substituted; or R², together with the adjacent nitrogen atom, Y and Ar, may form a condensed ring; or a salt thereof is useful as an agent for preventing or treating obesity, etc.