Prodeltaic sediment in the Gulf of Rosas, northwestern Mediterranean Sea is supplied mainly by the seasonally controlled Fluvia and Muga rivers and, until the seventeenth century, by a distributary of the southern located Ter River. These rivers, which had several distributaries in the past have developed a 120-km{sup 2} delta plain in a wave-dominated coast, prograding offshore by beach ridge development. High-resolution seismic profiles (3.5 kHz) and gravity cores were examined to evaluate the transgressive and highstand progradational history of prodelta deposits in the Gulf of Rosas. They cover an extension of about 365 km{sup 2} between the 20-m and 120-m isobaths. They extend 23 km offshore and, toward the south lie with the prodeltaic body of Ter River. Over a major flat erosional unconformity, related to postglacial Versilian transgression, the following pattern of seismic facies is seen progressing offshore: (1) stratified facies (5-15 m thick) with closely spaced southeastward-prograding reflectors, (2) chaotic facies (4-21 m thick) in which lenses with reflectors of low continuity and high acoustic amplitude predominate, and (3) thin transparent facies (2-7 m thick). An area of gas-charged sediment (90 km{sup 2}) is located between the 20 m and 80 m isobaths, mainly affecting the stratifiedmore » facies, from 2 to 6 m below the sediment/water interface. Sediment stratigraphy is well correlated, with the pattern of seismic facies showing a complex pattern of coarsening- and fining-upward sequences. Since the last Holocene transgressive stage and the following establishment of the present sea level highstand, a regressive depositional wedge-shaped sequence has been prograding on the Gulf of Rosas continental shelf.« less