Development of a technico-economic optimization strategy of cogeneration systems of electricity/hydrogen. consists in finding an optimal efficiency of the generating cycle and heat delivery system. maximizing the energy production and minimizing the production costs. The first part of the paper is related to the development of a multiobjective optimization library (MULTIGEN) to tackle all types of problems arising from cogeneration After a literature review for identifying the most efficient methods. the MULTIGEN library is described. and the innovative points are listed. A new stopping criterion, based oil the stagnation of the Pareto front. may lead to significant decrease Of computational times, particularly in the case of problems involving only integer variables. Two practical examples are presented in the last section The former is devoted to a bicriteria optimization of both exergy destruction and total cost of the plant, for a generating cycle coupled with a Very High Temperature Reactor (VHTR) The second example consists in designing the heat exchanger of the generating turbomachine. Three criteria are optimized the exchange surface, the exergy destruction and the number of exchange modules (C) 2009 Elsevier Ltd. All rights reserved