The delta of the Po River is a sediment mass derived by the interaction between the fresh water and sediment that the river transports from its drainage basin in northern Italy and the marine forces encountered in the upper Adriatic Sea. The characteristic features of deltaic deposition are determined by several back ground conditions: (1) geology, geography, and hydrology of the drainage basin; (2) historical development of the delta; (3) hydrology of the modern distributaries; and (4) hydrographic conditions in the Adriatic Sea. Primary sources have been used to obtain a summary of these conditions. Significant parameters include a mountainous source area near the site of deltaic deposition, a freshwater discharge of nearly 1,500 cubic meters/second, a sediment load that consists predominantly of sand and silt, a tidal range of 60 centimeters, a quiet sea with high salinity water (38 %0), and a locus of deposition on a shallow shelf that subsides slowly in the viciniti’ of the delta. The artificial form of the modern delta is caused by manmade works constructed in historical times to control the distributaries. Today 60 percent of the river flow and 75 percent of the sediment load discharge through a single distributary. The delta advances in front of the controlled distributaries at rates that are very much higher than those that characterized the prehistoric delta. Hydrographic processes that act within the distributary mouths and in the Adriatic Sea near the delta control sediment deposition and dispersal. The paper provides a detailed study of distributary mouth hydrography during a period of above average flow. River water dilutes Adriatic seawater primarily at the surface in the upper Adriatic, because the moderately low tidal range and high river flow interact to produce a well-stratified salt-wedge system. High salinity water occurs near the bottom close to the shoreline. The distributary-mouth bar, with its crest near mean sea level, acts as a barrier to intrusion of salt water. Normally the salt wedge invades the distributaries only at high tide, and the river flushes it out during low tide, although during very low river flow salt water penetrates far upstream. The fresh river water flows up and over the distributary-mouth bar and the salt wedge with velocities that equal or exceed those in the river before it enters the delta region. These velocities make it possible for the river to transport sand into the sea. As soon as the fresh water leaves the distributary channel and spreads over the sea surface, its velocity begins to diminish. Sand drops from suspension and falls on the marine side of the distributary-mouth bar. Marine wind and wave currents mold the sand into a shallow platform whose seaward face advances across the shelf. In front of each distributary, a plume of nearly fresh and turbid water moves actively seaward; the plumes are defined by the boundaries between more rapidly and less rapidly moving water. As it spreads, the fresh water suspension becomes progressively saltier and thinner. Initially silt and clay particles remain in suspension, but as the velocity decreases particles of progressively smaller size drop from suspension and are deposited. Beneath the turbid plumes in front of the distributaries and around the periphery of the delta between distributaries there exists a water mass with salinities of 25 to 30 %. In front of the distributary it is 8 meters in thickness. Between distributaries it is thinner, and it thins progressively seaward. The pressure of fresh water rapidly discharging from the delta, forces this layer of intermediate salinity water to move seaward along a broad front. It transports fine-grained sediment at least as far as 30 kilometers from the delta. Profiles of salinity, temperature, and suspended sediment concentration obtained within the distributaries, in front of the delta, and in the Adriatic Sea illustrate the kinds of interactions between fresh and salt water that lead to sediment dispersal and deposition. This volume was based on a symposium, Deltaic Sedimentation, which was held at the AAPG/SEPM Annual Meeting in New Orleans, Louisiana on April 1965. Many geologists have become involved in studies of deltaic sediments and sedimentation processes. Some of the papers in this volume are based on detailed local studies of modern deltaic sedimentary sequences, on processes of deposition, and on physical and biological characteristics of the deltaic environments.