This application provides a method for treating a human subject afflicted with Parkinsons disease (PD) with a pharmaceutical composition comprising rasagiline or a pharmaceutically acceptable salt of rasagiline, and a pharmaceutically acceptable carrier, comprising the steps of: (i) obtaining a biological sample comprising a genome from the human subject afflicted with Parkinsons disease (ii) assaying the DNA or RNA of the biological sample from the human subject using a probe or a primer, to determine the diploid genotype of the human subject at single nucleotide polymorphism (SNP) rs1076560 or rs2283265 (iii) identifying the human subject as a predicted responder to rasagiline if the diploid genotype is CC at rs1076560, CC at rs2283265, or CC at both rs1076560 and rs2283265 and (iv) administering the pharmaceutical composition comprising rasagiline and a pharmaceutically acceptable carrier to the human subject if the human subject is identified as a predicted responder to rasagiline.