Abstract: Agents for the treatment of Parkinson's disease contain, as an active ingredient, a xanthine derivative or a pharmaceutically acceptable salt thereof. The xanthine derivative is represented by the formula: ##STR1## in which R.sup.1, R.sup.2 are R.sup.3 are independently hydrogen, lower alkyl, lower alkenyl, or lower alkynyl; and R.sup.4 represents cycloalkyl, --(CH.sub.2).sub.n --R.sup.5 (in which R.sup.5 represents substituted or unsubstituted aryl or a substituted or unsubstituted heterocyclic group; and n is an integer of 0 to 4), or ##STR2## in which Y.sup.1 and Y.sup.2 represent independently hydrogen, halogen, or lower alkyl; and Z represents substituted or unsubstituted aryl, ##STR3## in which R.sup.6 represents hydrogen, hydroxy, lower alkyl, lower alkoxy, halogen, nitro, or amino; and m represents an integer of 1 to 4, or a substituted or unsubstituted heterocyclic group; and X.sup.1 and X.sup.2 represent independently O or S.