Geophysical and geological investigations suggest processes of sedimentary accretion and evolution of a forearc basin in the Southern Hispaniola region. Several different sedimentological and structural domains are defined on multichannel seismic reflection lines offshore. Other domains, including pelagic abyssal plain, trench, accretionary wedge, and forearc basin, are identified in the onshore outcrops in Southern Hispaniola. Onland deposits of the pelagic and trench domains (Southern Peninsula and Enriquillo trough), located north of Beata Ridge, are considered slightly different from the offshore ones because of collision between the thick crusts of Beata Ridge and the Central Cordillera. Accretionary wedge and forearc basin domains (Sierra de Neiba, Sierra El Numero, San Cristobal basin) provide sedimentological and stratigraphical data concerning the evolution of the margin. Widespread distribution of Oligocene heterometric and polymicritic conglomerates indicate an "erosional crisis," which could date the beginning of collision processes to the west.