Teachers who implement new programs have often been observed to adapt them to suit their own teaching situations. This process of adaptation raises four important issues: (1) Can teachers replicate practices developed elsewhere? (2) Can they be equally effective in doing so? (3) Must adaptation occur for implementation to succeed? and (4) Can different kinds of adaptation be discerned, some valued and others not? To address these questions, this paper examines four studies of the change process whose research questions or findings pertain to the replication/adaptation issue: (1) the survey component of the Study of Dissemination Efforts Supporting School Improvement (a study of innovative practices supported by federal programs); (2) the field study component of this same study; (3) the Rand Change Agent Study (an examination of federal "seed money" programs); and (4) the SRI International Study of the National Diffusion Network. For each of these studies, an effort is made to ascertain how the innovation was defined, identify sources of information used to determine fidelity, define the unit of analysis, and summarize the findings. Thereafter, a cross-study examination is presented to discuss the differences in the above studies and to assess the ways in which they have collectively contributed to a better understanding of school improvement practices. (TE)