A method for modifying Parkinsons disease by periodically administering a pharmaceutical composition comprising a therapeutically effective amount of rasagiline or a pharmaceutically acceptable salt of rasagiline to the patient, thereby modifying the disease. The method includes reducing the rate of progression delaying the need for symptomatic anti-Parkinsonian therapy reducing the risk of a Parkinsons disease patient requiring symptomatic anti-Parkinsonian therapy and reducing the functional decline.
