(Wherein n is an integer of from 0 to 3; R.sup.1 is substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, a substituted or unsubstituted alicyclic heterocyclic group, or a substituted or unsubstituted aromatic heterocyclic group; R.sup.2 is halogen, substituted or unsubstituted lower alkyl, substituted or unsubstituted aryl, a substituted or unsubstituted alicyclic heterocyclic group, a substituted or unsubstituted aromatic heterocyclic group, --COR.sup.8, or the like; R.sup.3 and R.sup.4 may be the same or different, and each represents a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted aralkyl, --COR.sup.12, or the like) For example, provided are adenosine A.sub.2A receptor antagonists comprising, as the active ingredient, a thiazole derivative represented by a general formula (I), or a pharmaceutically acceptable salt thereof, and the like.