The group of paintings ascribed to the Master of Flemalle is one of the most outstanding and at the same time most enigmatic of early Netherlandish painting. Influential throughout the fifteenth-century, these works are nowadays regarded, together with those of the Van Eyck brothers, as a starting point of Northern renaissance art. Ever since these paintings were grouped together a hundred years ago, on the grounds of stylistical analysis, they have been the object of controversial scholarly debates, concerning the identity of the artist and the coherence and homogeneity of the oeuvre. This publication presupposes neither the most newly assumed identification of the artist with Robert Campin of Tournai nor the homogeneity of the oeuvre. Instead, the investigation concentrates on the individual works, starting with the eponymous paintings in Frankfurt. Using the whole range of art historical methods and the results of technical investigations, the study presents new conclusions regarding division of hands and dating. Furthermore, the sometimes complex relations between different works are investigated. Another important result of the study is the reconstruction of now dismembered ensembles.