The nature of the physical regime in the vicinity of the Rhine ROFI(Region Of Freshwater Influence) has been determined in a series of collaborative observations. Extensive surveys with shipboard profiling and undulating CTD systems have been used to complement time series observations with an array of moorings instrumented with current meters, transmissometers and fluorimeters to determine the time evolution of flow and structure. The observations reveal a highly variable system in which the influence of the freshwater input from the Rhine extends northeastwards from the source and out to 30km from the coast. The mean water column stability is controlled by the combined effect of tidal, wind and wave stirring which brought about complete vertical homogeneity. During periods of low stirring the water column is observed to re-stratify over the whole inshore region through the relaxation of the horizontal gradients under gravity and with the influence of rotation as in the model of Ou(1983). Strong semi-diurnal oscillations are superimposed on the mean stratification, occurring throughout the stratified region at times of reduced mixing. The amplitude of this semi-diurnal variation is of the same order as the mean stability and frequently results in conditions being mixed or nearly mixed once per tide. It is inferred that this semidiurnal variation results primarily from cross-shore tidal straining which interacts with the density gradient to induce stratification. This conceptual picture of the contributing processes is tested in a 1-d point model forced by the observed slopes and the local density gradients. The model exhibits the same qualitative behaviour as the observations, produces oscillations in stratification of the amplitude observed and confirms the critical role of cross-shore tidal straining. The large cross-shore shear under stratified conditions is identified with the change in ellipse configuration which is observed to occur between mixed and stratified conditions. The occurrence of semi-diurnal variations in stability in the Rhine ROFI is thus inferred to be a consequence of the development of mean stability whenever the horizontal density gradients relax in conditions of low stirring. The flow in the Rhine ROFI is dominated by tides with the M2 semi-major axis of the order of 0.8 ms-1. The wind-driven flow has a transfer factor between -1 and 3 % and the rotation varies with depth closely to Ekman theory. Stratification intensifies the wind response at the surface while the explained variance is reduced near the pycnocline. The density driven flow within this region is generally parallel to the coast (northeastwards) and with surface speeds, determined by the HF radar, of about 10 cms-1, while the vertical distribution closely follows the Heaps (1972) profile.