This document provides an agenda for a workshop titled "Using real-world data to find undiagnosed patients with rare diseases" hosted by IMS Health at the World Orphan Drug Congress from April 20-22 in Washington D.C. The workshop will explore how real-world data can help address underdiagnosis of rare diseases. Speakers will discuss using large-scale real-world data to transform understanding of rare diseases, and present case studies of companies leveraging real-world data. The workshop will also cover using predictive modeling of real-world data to identify undiagnosed rare disease patients and new engagement models with healthcare providers and payers to increase rare disease treatments.