Today, the sustainability of cities is a critical consideration in the development of modern societies. One important dimension of this concept is the influence of occupation intensity on resource consumption and its associated waste generation. Emergy analysis constitutes an appropriate methodology for evaluating the sustainability of cities, given that it integrates the different types of flows interacting in urban regions in a common basis of comparison, the solar emergy joule (seJ). In this study, emergy analysis was used to evaluate the environmental sustainability of the Island of Montreal, Canada, in 2005 and to compare its situation with that of other nine urban centers. Results indicate that the total emergy used in 2005 stood at 1.153×1023seJ, with renewable resources representing 3.2%, and a waste-to-emergy ratio of 0.09. In comparing the cities, it was observed that the empower density, an emergy measure for the intensity of activities, fell markedly when each inhabitant had about 300m2 or more of available land. Results for the Island of Montreal point to the need to improve the city's environmental performance. Particularly, the high empower density indicates that projects involving the re-development of recovered areas provide a significant opportunity for attaining this objective.