The paper outlines an approach to concept design that integrates the development of the design specification with multi-objective concept development. ‘Excursions’ are undertaken to explore particular aspects of the design, e.g., reliability, in order to help create a concept that is strong in the salient design requirements. The paper then considers reliability as a principal design requirement. Existing reliability evaluation methods are reviewed with respect to their suitability for use in concept design. The paper then describes an approach, an ‘excursion’, that can be used to improve the reliability of a concept. The reliability excursion comprises a systematic method of evaluation and a reliability analysis toolbox. The research reported is an element of a larger concept design activity that itself forms part of a substantial project on integrated product design undertaken at the Polhem Laboratory, Lulea Technical University, Sweden and at UMIST, UK.