Adult learning theory, first described by Malcolm Knowles in the early 1970s, is based on a number of apparently self-evident axioms about how adults learn. The fundamental assumptions remain largely untested, and a critical analysis suggests that they may be largely a product of the environment in which adults find themselves rather than of any innate differences between adults and children. What evidence does exist suggests that one critical component of adult learning, self-assessment, is not easy. Further, while students can learn the skills to learn on their own (i.e., can acquire self-directed learning skills), this does not translate into greater competence, in either the short or long term. Uncritical reliance on the principles of adult learning may have detrimental consequences, particularly in the domain of maintenance of competence.