An estimated 60-80% of the chance to develop Alzheimer’s disease depends on genetic factors, and similar percentages apply to other neurodegenerative diseases. Thousands of genetic risk factors are involved: some occur only very rarely in the population, while others are more common. A persons’ risk for developing diseases depends on the unique constellation of genetic variants they inherited from their parents. Knowing exactly what genetic factors are involved will help uncover molecular processes underlying the disease, which is necessary to design effective treatment or prevention strategies. Knowing the pattern of disease-associated genetic variants can also be used to predict an individual’s vulnerability for diseases, far before the onset of symptoms. In the future, when treatment options become available, predicting who is at risk before the onset of symptoms will allow timely and accurate treatment and/or prevention.