The ISO 14000 series of standards will include guidelines for product life-cycle assessment (LCA) that are intended to be applicable to all products, regardless of materials, production system, or end use. Practice in LCA, however, has lagged far behind theory. Existing methods are at best marginally applicable to high-technology manufactured products such as automobiles that can contain thousands of components made from hundreds of raw materials. Optimization of the environmental performance of such production systems cannot be reduced to simple measures of energy and material use. This paper identifies technical issues relevant to the development operational LCA methodologies for high-technology products and proposes a hierarchical approach that is consistent with the general principles of ISO 14000 but is tailored to the needs of LCA users within high-technology industries.