These are the proceedings of the symposium Medieval Murals in the Church Attics of Östergötland, held in September 2015, at Norrköping Art Museum, organised by ICOMOS Sweden¿s Scientific Working Group for Mural Paintings. The purpose of the symposium was to bring different disciplines together to shed light on diverse aspects of an ensemble of medieval wall paintings, located in the attics of eight churches in the county of Östergötland in south-east Sweden. This ensemble of medieval art, hidden in the attics of the churches, offers a rare opportunity for gaining new insights into sacred art. The absence of a complex conservation history makes this medieval wall painting ensemble unique. The paintings are thus an extraordinary historical source of information about medieval art and the messages embedded in the materials. An art-technological approach was applied in recent investigations of these mural paintings. Interesting results were obtained by exploring the material composition and its effects on the visual appearance. Through a collaborative effort, the messages and significance of the paintings, which present-day viewers cannot perceive, may again become accessible. The contributors to the proceedings share their experience, insights, and opportunities related to art-technology, value and the reception history of this type of sacred art in historic churches.