The research sets out new information on a group of medieval wall paintings made in the fifteenth and sixteenth centuries in the Diocese of Turku. The paitings have been attributed to church builders and they form a portion of their work. The research examines the actual wall paintings in about thirty medieval stone churches, the workshops that executed them and the visual practices which governed the making. In addition, light is shed on both Diocesan and parochial contexts for the images and image-making, and the ways in which they were connected to the political, economic and local endeavours in the Diocese of Turku. The research seeks to explore new ways to approach the paintings, long regarded as theoretically difficult visual material in the context of Finnish medieval art.