RET genetic testing affords valid clinical strategies in the diagnosis and management of MEN 2. For at risk family members, the test provides accurate diagnosis of gene carriers and best chance of cure of medullary thyroid carcinoma by prophylactic total thyroidectomy. The test results, however, may have medical, psychological, ethical, and social effects on the individuals as well as their families, it is important for an individual to know the potential consequences and to give an informed consent before having the genetic test. Health care providers should make efforts to be aware of these potential effects and to support a tested individual throughout the entire screening process.