Premised on the view that students with more years of Montessori education (MEY) would possess to a higher degree those qualities emphasized in the Montessori environment and that Montessori students would be as successful as students more traditionally educated, this report presents the final assessment for the Longitudinal Assessment Study, initiated in 1986 to assess the effects of a Montessori education into adulthood. All participants attended the Franciscan Montessori Early School in Portland, Oregon and ranged in age from 16 to 27 years at the time of this assessment. Over a period of 18 years, 6 assessment cycles were conducted approximately once every 3 years, the first 4 focusing on quantitative information from surveys and personality and achievement tests, and the later 2 focusing on qualitative information from surveys using open-ended questions. For the later two assessments, the sample was split into three groups varying in the years of Montessori education: (1) few MEY (3-5 years); (2) some MEY (6-9 years); and (3) many MEY (10-16 years). The report describes the history and previous findings and discusses the impact of participant dropout. Findings are presented for demographics (including academic attainment, academic aspiration, living situation, and career goals) and attitudes and behaviors (judgment of parents' decision to send them to a Montessori school, approach to education, and "Montessori-like" personality or behavior). The report concludes by noting that even when sample bias was taken into account, a Montessori education was a key positive factor in the participants' academic, personal, and social development and is an important factor in their current identity. Some aspects of a Montessori education were related to short-term problems. The report suggests that families come to a Montessori education with a Montessori-like life philosophy emphasizing independence, lifelong learning, cooperation over competition, understanding over memorization, and self-direction and understanding. Several participants reported that the Montessori-combined academic and social approach was important in learning how to learn beyond high school and college. (Ten appendices include the Cycle 6 survey, verbatim open-ended participant comments, and data summaries.) (KB)