The first Montessori school was founded in Rome in 1907. There was interest in Montessori's methods in the United States between 1910 and 1920, but these methods were forgotten until after 1950, when a second Montessori movement began in the United States. Some schools with Montessori programs are affiliated with the Association Montessori Internationale or the American Montessori Society. Most public elementary schools, however, have no such affiliation. Characteristics of elementary Montessori schools include: (1) students' involvement in individual or small group activity of their choice; (2) an attitude of cooperation rather than competition; (3) an emphasis on student's individual responsibility; and (4) a 3-year range in the age of students. Data from a study of 63 school districts that offered Montessori programs during school year 1990-91 are cited. Problems related to the implementation of Montessori programs in public schools are then discussed. One problem is that of admission criteria, especially the question of whether only children who have had preschool Montessori experience should be enrolled in elementary Montessori programs. However, the greatest problem in starting and maintaining a public school Montessori program is the lack of qualified teachers. Research indicates that in spite of these difficulties, Montessori programs are a popular alternative to traditional public school education. (BC)