Findings of a study that examined school organizational change associated with the implementation of open enrollment in Minnesota are presented in this paper. Data were derived from mailed surveys completed by 126 principals at the end of the 1989-90 school year. A three-way multivariate research design with seven dependent variables was used to estimate differences in open-enrollment effects between participating and nonparticipating schools, large and small schools, and rural and urban schools. Findings indicate that open enrollment has: (1) created a market system for educational services; (2) stimulated improvements in curricula and support services; (3) promoted greater parent and teacher involvement in school planning and decision making; (4) fostered a more equitable distribution of school resources and student access to educational services; and (5) increased the ethnic and cultural diversity of schools. Open enrollment had a greater impact on large and rural schools. Rural schools experienced a greater amount of organizational change than urban schools and have expanded their curriculum and service programs to the limit of their resources. The pattern of organizational change suggests that most open-enrollment effects tend to diminish with experience in the program, especially in the case of parent/teacher influence on school management, but they do not return to preprogram levels. Sustained effects in school improvement and specialization in educational programming are noted. School type and wealth do not appear to be associated with school organizational change in response to open enrollment. Four figures and eight tables are included. (Contains 66 references.) (Author/LMI)