Public elementary and secondary schools in Illinois that have remained stably racially mixed over time are identified in this study. The neighborhood characteristics, pupil assignment policies, instructional programs, and other circumstances that have contributed to that stability are also determined. Several alternative definitions of "stable racial mix" are given, and these definitions are then applied to enrollment statistics for every public school in Illinois. Illinois schools meeting stated criteria are then classified according to various enrollment and locational attributes. From this universe, forty schools are selected for a detailed field investigation and personal interviews. Conclusions are derived regarding those factors which appear to promote stable racial mix under a variety of community and neighborhood circumstances. The applicability of desegregation techniques and the lessons learned from their implementation in the forty case study schools to additional Illinois schools are also considered. Topics meriting further research are suggested. (Author/AM)