Data from moored instruments and transects were used to examine water renewal within the 3 basins of the Saguenay Fjord (Québec, Canada). Spring freshet affecting the Saint Lawrence River resulted in a new temperature and salinity signature in the fjord, indicative of a renewal event. The data suggest that a large proportion of the waters within the fjord are replaced within less than 2 months, confirming a short residence time. Data collected just inside the mouth of the fjord showed that these waters were mostly of Saint Lawrence Estuary origin. Measurements at low tide in the first (external) basin of the fjord indicated a mix of the lowest salinity waters observed at the sill during a tidal cycle and Saguenay River surface water. This mixture subsequently forces renewal events of surface and intermediate waters in the inner basin. The range of salinities observed at the sill are similar to those found at a depth of 20 to 70 m, approximately 100 km further northeast in the Saint Lawrence Estuary. The synchronous variation in salinity at the 2 sites suggest the simultaneous vertical movement of waters within the estuary, and that it is this movement that is a determining factor for the type and speed of renewal events within the Saguenay Fjord.