This study is the fifth assessment in an 18-year longitudinal study begun in 1986 to follow a group of Montessori students who attended the Franciscan Montessori Earth School in Portland, Oregon. Participating were 45 students with an average age of 18 years, about half of whom were in high school and half in college. Students completed an online survey focusing on psychological, social, and vocational issues. The study postulated two hypotheses: (1) the number of Montessori Education Years (MEY) would positively relate to qualities emphasized in Montessori education; and (2) participants with any Montessori education would be at least as successful as the general population. Findings provided considerable support for the first hypothesis, tempered by drop-out sample bias, in terms of life-long learning and self-development. The personal value of life-long learning was identified as most prevalent among students with 10-15 MEY. The striving for self-development was manifested by a strong desire for self-understanding, general personality development, self-direction and discipline, and a strong positive attitude toward social-interactive activities. Evidence that participants with 10-15 and 3-5 MEY were more similar in comparison to participants with 6-9 MEY suggests that the most important factor is a natural predisposition toward a Montessori-compatible lifestyle. The evidence supporting the second hypothesis was strong, with some negative effects reported. (Nine appendices include comments from participants regarding career-oriented volunteer and paid experience, educational philosophy, maximizing the ability to learn, and projective stories. A copy of the online survey is also included.) (KB)