As a conclusion to this book on informal learning at work, this chapter offers a reflective appraisal of the contributions of the various researchers. Two questions form the guiding principle of this reflection. (1) Do the contributions of the researchers in this publication lead to (more) conceptual clarity with respect to the concept of “informal learning at work”? (2) Is it possible, on the basis of the articles, to develop one single universal and empirically founded theoretical framework or model? The author’s definition and the constructed mode, which is based on reviews of the international literature and produced between 2000 and 2008, is taken here as point of reference. Although informal learning at work is a diffuse and complex phenomenon, making it difficult to define, the author concludes that progress has been made in achieving an unequivocal definition. The recorded studies bring to light not only variables that have not been previously studied, but also the empirical verification of these and the variables already considered to be relevant. The results of these studies are being used to improve the theoretical framework initially developed by the author. However, this does not mean that one single comprehensive and universal model is established as a result. After all, the chapters in this book indicate that research in specific contexts and/or with specific theoretical approaches for the selection and the measurement of variables produce partially different and partially related theoretical frameworks. The chapter concludes with suggestions for further research.