Results are reported from an investigation of the implementation and effects of The Adaptive Learning Environments Model (ALEM), a program designed to provide special education services for mainstreamed handicapped students in regular classroom settings on a full-time basis. ALEM includes components of prescriptive instruction with informal approaches to foster inquiry, independence, and social cooperation. Effects of implementing ALEM in 26 mainstreaming classrooms were evaluated via measurements of degree of program implementation, classroom process outcomes, student academic and attitudinal outcomes, and teacher and parent attitudes and assessments. Results are detailed for four major topics: degree of program implementation, relationship between implementation and selected student outcomes, relationship between degree of program implementation and classroom processes, and teacher and parent attitudes and assessment of program impact. Overall, results supported the feasibility and efficacy of a full time mainstreaming approach for moderately handicapped students in the ALEM classrooms. Among policy implications noted is that more restrictive placement should be considered only after a full time mainstreaming approach has been tried and found ineffective. (CL)