A long-held goal in oncology has been to develop therapies that target the specific abnormalities in each patient's cancer rather than simply treating cancers based on the tissue of origin. In the past decade, advances in technology have enabled researchers to relatively quickly and inexpensively determine, in minute detail, the genetic makeup of tumors. Although relatively few targeted cancer therapies are currently available in the clinic and it is not yet clear whether all cancers are driven by genetic changes that can be targeted, there is widespread optimism in the cancer community that this new ability to assess the genetic abnormalities in tumors will ultimately lead to better cancer treatments and improved patient outcomes. Policy Issues in the Development and Adoption of Biomarkers for Molecularly Targeted Cancer Therapies is the summary of a workshop convened in November 2014 by the Institute of Medicine's National Cancer Policy Forum to discuss recent trends in the development and implementation of molecularly targeted cancer therapies and explore potential policy actions to address specific challenges. This report highlights the presentations and discussions at the workshop.