Abstract: Conventionalreliability analysis is based on the probabilistic distribution ofrandom variables. In structural design problems, however,statistical data regarding load or resistance are usuallyincomplete. In addition, a robust structural design must considerthe interaction of the structures with the environment, errors inthe stage of the structure design, the structure analysis, theevaluation, and the fabrication, some of which may not becategorized as to randomness. Therefore, a new theoreticalframework for the structural reliability and the optimal designwhich incorporates the different uncertainty sources becomesnecessary to achieve a suitable practical solution different fromthe traditional probabilistic method. This paper provides anoverview on structural reliability and optimal design undercircumstances of incomplete information. Several topics such asprobability-based design, possibility theory for dealing withincomplete information, the influence of model errors andsubjective uncertainties, and applications of evolutionaryalgorithms to reliability design are discussed. The paperconcludes with a brief perspective for further research.