The term" impostor phenomenon" is used to designate an internal experience of intellectual phoniness that appears to be particularly prevalent and intense among a select sample of high achieving women. Certain early family dynamics and later introjection of societal sex-role stereotyping appear to contribute significantly to the development of the impostor phenomenon. Despite outstanding academic and professional accomplishments, women who experience the impostor phenomenon persist in believing that they are really not bright and have fooled anyone who thinks otherwise. Numerous achievements, which one might expect to provide ample objective evidence of superior intellectual functioning, do not appear to affect the impostor belief. Four factors that contribute to the maintenance of impostor feelings over time are explored. Therapeutic approaches found to be effective in helping women change the impostor self-concept are described.(7 ref)(PsycINFO Database Record (c) 2017 APA, all rights reserved)