The need to investigate the role of suspended sediments in the transport and fate of chemical contaminates in the St. Lawrence estuary has led to the measurement of profiles of suspended sediments, horizontal current, temperature, and salinity at an anchor station apprximately 60 km downstream from the turbidity maximum. Hourly profiles over nearly three semidiurnal tidal cycles reveal peaks of suspended sediment concentration following maximum flood and ebb currents at the bottom, whereas near the surface there is only one maximum in suspended sediment concentrations per tidal cycle. Observations of the distributions of suspended sediment and its horizontal flux suggest that local resuspension is the controlling factor at the measurement site. This study demonstrates that landward sediment flux in the lower layer is maintained by the ebb-flood asymmetry mechanism described by Dronkers (1986) and by the asymmetry in vertical mixing due to fluctuations in stratification related to the intrusion of the salt wedge. The latter mechanism is explored in detail by means of a vertical transport model for fine-grained newly deposited sediments. The model employing standard prescriptions for mixing and resuspension results in the best match between simulated and observed sediment distributions for a particle sinking velocity of 3¿10-4 m/s. This settling rate corresponds to a mean particle size of 15 μm, which compares closely with the average observed particle size of 10 to 20 μm (Krank, 1979). ¿ American Geophysical Union 1989