The sequence stratigraphical depositional model has concentrated primarily on eustasy and tectonic subsidence as the dominant controls on sequence development, with variations in other factors such as sediment supply playing only a modifying part. Little consideration has been given to the significance of the uniqueness problem to the model predictions. Thus it is often assumed that if the sequence stratigraphical model can provide a simple fit with the available data, then it must be the correct and unique solution. This is rarely likely to be the case. Using a quantitative forward model it is possible to reproduce the basic geometries of type 1 and type 2 sequences and then to assess, via a series of sensitivity tests, the significance of some other controls. Use of this forward-modelling approach suggests that fluvial profile behaviour is a first-order control on sequence geometries. It also suggests that variations in the magnitude of sediment supply can significantly alter the development of transgressive ravinement surfaces. These two examples highlight the importance of the uniqueness problem to the sequence stratigraphical model.