Snow\'s conceptualization of aptitude has been revisited and expended by many researchers, including Standford Aptitude Seminar, during last 6 years since his demise. The purpose of this article was to present a brief overview on the change of Snow\'s concept of aptitude during his life and his suggestion about future aptitude research. 1) Chronical description was made on Snow\'s ATI research and the development of his theory on aptitude. 2) On each step of the development, it was examined that what were the strong points and limitationas that his research and theory had. 3) It was explored that what would be the possibilities and limitations in future research on aptitude.