This article reports on the presentations and discussions of the workshop on “Adaptive Object-Models and Metamodeling Techniques”, held in conjonction with Ecoop’01 in Budapest on June 2001. After overviewing the themes of the workshop, its organization is briefly presented. This is followed by a summary of the works presented and a section dedicated to develop the results of the workshop. The main conclusions are about comparing and locating one towards another three techniques of interest: — Reflection at the Language Level, — Adaptive Object-Models and — Meta-Tool Approaches to Meta-modeling. Moreover, a discussion on the needed levels of abstraction, and on their nature, is also developed in reference to the so-called “OMG four-layer architecture”.