Adults learn from many sources, such as volunteer work, community services, homemaking, jobs, and other activities, and they increasingly want this learning to be recognized so that they can reenter the job market, get a promotion, or return to college. Therefore, scientific methods have been developed to help adults document their experiential learning. Among the main ways to assess prior experiential learning, the portfolio seems to be the most flexible and the most accurate. Other methods include testing, either by individual teachers or by standardized tests, and interviews. One of the basic principles of recognition of prior learning is to award credit only where credit is due in direct relation to education and/or working objectives. Recognition of prior learning has been successfully implemented in the United States, and the U.S. is now in the final stage of the overall process, which is the standardization of evaluation criteria. One principle must remain fixed: recognition must be given for learning outcomes in relation to goals by experts whose competence is evident using scientifically proven methods. (Examples of methods of recognizing prior learning in colleges in the U.S. are given in this paper.) (KC)