This study investigated the changes in the mainstreaming practices of five school districts, which were originally described in a 1974 study by Birch. The districts involved were: Tacoma (Washington), Richardson (Texas), Plano (Texas), Tucson (Arizona), and Louisville (Kentucky). Survey forms were sent to superintendents of the original six districts of which the above five responded. In the original study, each district displayed unique attributes in its approach to mainstreaming and this remained true in the follow-up study. Four important factors emerged in relation to mainstreaming: (1) teacher preparation; (2) placement and services for students with disabilities; (3) attitudes toward mainstreaming; and (4) cost of mainstreaming. Although some students with mild mental deficiency (MMD) spent nearly 100 percent of their time in the general education setting, each district still maintained self-contained and resource rooms for those students unable to be integrated into the general education setting. Other findings indicated that the cost of segregated classes for students with disabilities in 1994 exceeded the cost of segregated classes in 1974; that it cost less to service MMD students in self-contained classes in 1974 than in general education classes in 1994. There were no favorable statements from any respondents regarding the costs of mainstreaming. (Contains 22 references.) (DB)