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This first sedimentary interpretation of two incised-valley fills in the Gulf of Cadiz (southern Spain), which accumulated during the last fourth-order eustatic cycle in response to fluvial incision, changes of sea level, and correlative deposition, relates the filling of the estuarine basins and their barriers with four regional progradation phases, H-1 to H-4. The cases studied are the wave-dominated Guadalete, and the mixed, tide and wave-dominated Odiel-Tinto estuaries. The sequence boundary is a type-1 surface produced during the lowstand of the Last Glacial period ca. 18 000 C-14 yr BP. No fluvial lowstand deposits were found in the area. Due to rapid transgression the valley fills consist of transgressive and highstand sediments. The maximum landward advance of the estuarine barriers occurred ca. 6500-6000 C-14 yr BP during the maximum of the Flandrian transgression, but there is no evidence of sea level rising appreciably above the present. A large part of the estuaries was filled during H-1 (ca. 6500-4400 C-14 yr BP) but ravinement by shifting tidal inlets destroyed most of the coeval barriers. During the H-2 phase (ca. 4200-2550 C-14 yr BP) sedimentation was favoured by arid conditions and concentrated in the axial estuarine zones and the barriers. Between H-2 and H-3 prevailing winds changed from W to WSW, increasing spit growth to the east and south-east. Progradation of bay-head deltas and flood-plains during H-3 (ca. 2300-800 C-14 yr BP) and H-4 (500 yr ago to the present) further reduced the accommodation space in the largely-filled valleys, and sediment by-passed the estuaries and accumulated in the estuarine barriers as fast-growing spits. Arid conditions and increasing human activity have caused rapid coastal modifications.