Whether the physician's professional diagnoses and behaviors will meet the patient's best interests or not, is the most influential factor of patient's best benefits. In medical ethics, under the guideline of non-maleficence and beneficence, the physicians in addition to have an obligation to concern the patient's best interest to medical procedures, but also have to measure the patient's condition and take the balance between the risk of medical procedures and predictable patient's best interests. Therefore, this study comments many topics including the legal and ethical definitions of the best interests, the medical applications of the beneficence, and examples. The medical practitioners need to explore the maximum possible to concern the patient's autonomy and let patients participate in the medical decisions. Begin with the values of the parties and an equal or better life quality to let the medical decision-making base on the patient's best interests.