The perceptions of 355 principals, regular classroom teachers, and special education teachers regarding the extent of implementation of administrative practices pertaining to the mainstreaming of mildly handicapped children in Mississippi were studied. The results indicated that the first year of mainstreaming in Mississippi saw only moderate implementation of administrative practices considered essential to effective mainstreaming programs. Analysis identified three areas where the perceptions of the three groups of professionals were not congruent (whether or not the principal should become cognizant of the characteristics of mildly handicapped children, whether or not community resources should be utilized in exceptional child education, and whether or not teachers should be encouraged to educate children about handicaps), thus indicating a need for cooperative planning in developing a rationale for mainstreaming mildly handicapped children in the years ahead. (Author/DLS)