The learned professional exemption is restricted to professions where specialized academic training is a standard prerequisite for entrance into the profession. The best evidence of meeting this requirement is having the appropriate academic degree. However, the word "customarily" means the exemption may be available to employees in such professions who have substantially the same knowledge level and perform substantially the same work as the degreed employees, but who attained the advanced knowledge through a combination of work experience and intellectual instruction. This exemption does not apply to occupations in which most employees acquire their skill by experience rather than by advanced specialized intellectual instruction. The FLSA distinguishes the exercise of judgment and discretion from the application of particular skills, even high-level skills. A lumber grader, for example, may be highly trained in distinguishing subtle variations in wood but is not performing professionally exempt job duties.