Marquard's works on the eucharist are compared with the more important contemporary works on the topic, notably Matthaeus of Cracow's Dialogus rationis et conscientiae. It is argued that both Matthaeus' Dialogus and Marquard's Eucharistietraktat, the two most successful late medieval works on the eucharist in Latin and German respectively, were both reacting in different ways to a dominant climate of fear expressed towards sacramental reception. The chapter then considers in detail a series of further problematic issues of eucharistic theology and its instruction in the later Middle Ages on which Marquard makes a significant contribution: the use of miracle narratives in teaching the theology of transubstantiation; the permissible frequency of sacramental reception; the role of the eucharist in achieving mystical union; the perception of physical sweetness in the sacrament; and the broad complex of eucharistic visions, manifestations of the holy blood, and other kinds of transformation.