This special issue arises from the observation that modern product development often involves complex analyses from multiple disciplines, consideration from product life cycle aspects, making difficult tradeoff decisions and in the meantime, achieving optimal product design at the lowest costs and in the shortest time. To systematically integrate various design perspectives to achieve the optimal design is a very challenging task. Such an integration and optimisation capability is in great demand and potentially of a significant benefit to all manufacturing industries. Design space exploration and optimisation is an important and often necessary step in product development. Research in this area has yielded many promising approaches and strategies. This special issue of IJPD was intended to present the state of the art in this area and promote further research in order to provide engineers with practical tools that support integration and optimisation.