This study uses the life cycle assessment methodology to analyze the type and origin of environmental impacts related to natural gas distribution networks in high and low density neighborhoods, and compares the environmental performance of two infrastructures in low density neighborhoods: a standard natural gas grid and a discontinuous system based on propane tanks. The results show that the impact per dwelling in the environmental categories studied is between 1.9 and 4.8 times higher in a low density neighborhood, depending on the impact category. Besides, in high density areas the main impact originates from components and materials related to the buildings and dwellings, whereas in low density areas the main impact originates on the neighborhood network. Given this last result, the advisability of substituting the neighborhood network by a discontinuous system based on propane tanks has been evaluated, obtaining as a result that when a single neighborhood pipe, longer than I km, is required to reach one user, it is environmentally preferable for all the studied environmental categories to use the propane tank system. (C) 2008 Elsevier Ltd. All rights reserved.