This paper proposes the multi-objective optimization of the design of natural gas transmission networks to support the decision of regulatory authorities. The problem formulation involves two objective functions: the minimization of the transportation fare and the maximization of the transported gas volume. These design parameters of the pipeline project must be previously established by the regulatory agency, considering an attractive return on the investment for the entrepreneurs and the demands of current and future consumers. The solution of this problem without an optimization tool may imply in unfair gas prices or the lack of investors interest. The proposed analysis is focused on growing markets, associated to a continuous increase of the natural gas consumption. Constraints associated to gas flow and compressor stations guarantee the feasibility of the set of design options found. Aiming to illustrate the performance of the proposed approach, the tool was applied to a typical trunkline example. (C) 2016 Published by Elsevier Ltd.