We have pleasure in presenting Volume Fourteen to our readers. Volume Fourteen signifies a new dimension for our series, a volume devoted to the development of a single timely topic, that of sensitivity to uncertainty. This is still a broad topic and has been treated as such by the se­ veral distinguished authors contributing to the volume from their extensive experience both in theory and practice. While the theme running through the volume emphasizes uncertainties in areas related to reactor physics, it is true to say that this field of application has much to offer other disciplines as well. Some of the authors are engaged in ex­ tensions to other areas. The volume may therefore appeal to a much wider audience who will appreciate a single and compre­ hensive overview of a methodology that is applicable to other fields. Notable developments in the field of nuclear engineering have included the formatting in recent versions of Evaluated Nuclear Data Files (e.g., ENDF/B and its variants) of cross­ section uncertainty, the general acceptance of good practice in the representation of error correlation matrices, and more recent developments in the application of Monte Carlo tech­ niques to sensitivity analysis in complex geometries.