We have witnessed remarkable progress in the diagnosis and treatment of diseases over the past century. Yet, a close examination of this progress reveals a tremendous unevenness in developments across different fields. The aim of this project is to develop detailed, empirical studies of specific disease categories that will help us understand the factors behind this uneven progress. Areas of concentration will include cardiovascular disease, cancer, and mental health. These studies will provide insights into unexpected sources of learning. Moreover, they will explore one of the main hypotheses of our study: if feedback mechanisms between “learning by doing” and bench research are effective, progress will occur more rapidly; if these feedback mechanisms are ineffective, progress will be slower. These disease studies will also explore which institutional environments foster effective feedback mechanisms, and how these interactions are affected by public policy. Our ongoing collaboration with the Merck-supported European Pharmaceutical Regulatory and Innovation Systems (EPRIS) should enable us to make careful cross-national comparisons.