A numerical model is developed to analyze the stability and propagation characteristics of coastally trapped waves on a shelf with a shelf edge density front. The model is applied to the Saglek Bank on the Labrador Shelf in an attempt to explain the ice edge undulations observed in NOAA 5 satellite images. It was found that the instability is suppressed by the bottom slope if the entire shelf slope is below the front. However, if the front intersects the bottom at about 1000-m depth with an associated current speed of 50 cm s-1 (an upper limit for the Labrador Current), the front could be unstable with a wavelength of 70--90 km and phase speed of 30--45 cm s-1, in approximate agreement with the estimates from satellite images. Furthermore, the neutral propagating modes will be modified by the front. Some modes will be transformed from barotropic shelf waves to bottom-trapped frontal waves. The presence of a density front on a continental shelf also results in either restricting or eliminating the backward propagation of energy on the shelf and hence has a significant effect on the energy propagation along the shelf. ¿ American Geophysical Union 1988