In this paper a tabu search algorithm is proposed for the optimization of constrained gas distribution networks. The problem consists in finding the least cost combination of diameters, from a discrete set of commercially available ones, for the pipes of a given gas network, satisfying the constraints related to minimum pressure requirements and upstream pipe conditions. Since this is a nonlinear mixed integer problem, metaheuristic approaches seem to be more suitable and to provide better results than classical optimization methods. In this work, a tabu search heuristics is applied to the problem and the results of the proposed algorithm are compared with the results of a genetic algorithm and two other versions of tabu search algorithms. The results are very promising, regarding both quality of solutions and computational time.