Clay mineralogy Is controlled in the Campo de Gibraltar flyschs by some paleoenvironmental and dlagenetic factors, which appear differently reflected in the several units and lithologies. In fine-grained beds, clay minerals are mainly detrltal in origin and, consequently, they can be used as indicators of sources. In this work, the main detrital associations established from previous mineralogical and geochemical studies are described, and the influence of the possible sources is analysed. The obtained results confirm in some cases the previous interpretations, while in other cases led us to question either the proposed sources or the assumed paleogeographic relations between some of these units