Direct DNA tests for mutations in neurogenetic disorders are establishing a new era in diagnostic neurology. These highly accurate and specific tests will greatly improve diagnosis and genetic counseling, lead to more accurate assessment of prognosis, and reduce the cost of diagnostic evaluations. However, the use and interpretation of the tests can be complicated, and there are numerous social, psychological, and ethical implications of the testing that need to be recognized and anticipated. To provide the best care for our patients, neurologists need to understand the benefits and risks of this testing and properly apply it in the context of each individual clinical situation.