Due primarily to developments in immunology, chemotherapy and hygiene the estimated life expectancy at birth increased during the last century from about 55 years to 80 years. Since the human Technical Life Span (TLSh) is about 120 years and life expectancy is today steadily increasing by about 2.2 months/year, a life span of 100 years may appear quite soon. Knoll developed (-)-deprenyl, the first anti-aging drug, the prophylactic administration of which increased significantly the average life span of animals. (-)-Deprenyl became a world-wide used experimental tool as the first selective inhibitor of B-type MAO and being the unique MAO inhibitor free of the cheese effect was introduced to treat Parkinson's disease, because it could be administered in combination with levodopa without side effects. However, Knoll demonstrated in his later work that (-)-deprenyl has enhancing qualities already in femto-picomolar concentrations, which leave MAO-B activity unchanged, and the activity of the catecholaminergic neurons in the brain stem and this previously unknown 'enhancer effect' is responsible for the peculiar therapeutic benefits caused by (-)-deprenyl. Knoll proposed 25 years ago to slow the aging of the brain, the decay of behavioral performance, prolong life, and prevent or delay the onset of age-related neurodegenerative diseases such as Parkinson's and Alzheimer's via the prophylactic daily administration of 1 mg (-)-deprenyl. At present (-)-deprenyl belongs to the best known anti-aging drugs and a rapidly growing number of people are already trying to slow the aging of their brain by taking (-)-deprenyl as a prophylactic agent. Nevertheless, up to the present, an exact analysis with placebo control of the capacity of (-)-deprenyl to prevent or delay the onset of neurodegenerative diseases is still missing. It is already very much on the map to perform such a study with this world-wide highly esteemed Hungarian drug.