Promotions of officers of the Regular Corps to any grade up to and including the director grade shall be either permanent promotions based on length of service, other permanent promotions to fill vacancies, or temporary promotions. Permanent promotions shall be made by the President, and temporary promotions shall be made by the President. Each permanent promotion shall be to the next higher grade, and shall be made only after examination given in accordance with regulations of the President.

The President may by regulation provide that in a specified professional category permanent promotions to the senior grade, or to both the full grade and the senior grade, shall be made only if there are vacancies in such grade. A grade in any category with respect to which such regulations have been issued is referred to in this section as a “restricted grade”.

Examinations to determine qualification for permanent promotions may be either noncompetitive or competitive, as the Surgeon General shall in each case determine; except that examinations for promotions to the assistant or senior assistant grade shall in all cases be noncompetitive. The officers to be examined shall be selected by the Surgeon General from the professional category, and in the order of seniority in the grade, from which promotion is to be recommended. In the case of a competitive examination the Surgeon General shall determine in advance of the examination the number (which may be one or more) of officers who, after passing the examination, will be recommended to the President for promotion; but if the examination is one for promotions based on length of service, or is one for promotions to fill vacancies other than vacancies in the director grade or in a restricted grade, such number shall not be less than 80 per centum of the number of officers to be examined.