This paper discusses the fresco decoration of Santa Maria ad Cryptas. The frescoes are described and analyzed, and then compared to similar programs in order to determine which features are based on earlier sources, and which are unusual or unique to this particular church. The traditional features are found to reflect a long-established pattern of church decoration reflected in such monuments as Old Saint Peter’s, Sant’Angelo in Formis, the Cathedral of Monreale, and the Cappella Palatina. The unusual features (including the placement of the Passion cycle in the presbytery, and the location of the Crucifixion over the altar) are explained as modifications that emphasize themes of local importance, or of special significance to the patron. The Fossa frescoes utilize programmatic elements, such as the Old and New Testament narrative cycles, to explain sacred history as it related to a medieval man of the patron’s class and profession.