To better understand transparency in philanthropy — both its meaning and the current state of practice among foundations — CEP analyzed survey data from 145 foundation CEOs and more than 15,000 grantees and systematically reviewed more than 70 foundation websites. This report reveals that funders see grantees as the primary audiences for their transparency efforts, and both foundations and grantees believe transparency about the substance of foundation work, rather than about financial disclosures or governance, matters most to effectiveness.