Products that incorporate materials manufactured at the nano scale (i.e., nanoproducts) offer many potential benefits to society; however, these benefits must be weighed against potential costs to the environment and public health. This document was developed to provide a broad guidance for assessing the sustainability of nanoproducts and is intended to lay the groundwork for developing a decision-support framework through continual updates as research in this area progresses. At the very least, it will aid stakeholders when navigating the various choices that must be made to foster the development of sustainable nanotechnology. Given the all-encompassing nature of sustainability, this work should be of interest to stakeholders in all areas of nanotechnology, including research, product development, consumer use, and regulation. The aim of this work is not to make decisions for stakeholders, but to help frame the pertinent issues that must be addressed to properly assess emerging nanotechnologies and to provide information on the various tools that may be used to address them. The foundation of this approach is to consider existing standards and methods for environmental, economic, and social assessments using a life cycle perspective and offer guidance by relaying first-hand knowledge of applying assessment tools to nanotechnologies, whenever possible. Brief overviews of the various assessment methodologies are provided to help stakeholders make informed choices when selecting tools appropriate for their goals. For specific details of a method, readers are directed to the referenced standards and guidance documents supporting the application of these tools. The key steps to be included in the evolving framework include: characterizing a nanoproduct and identifying potential risks and impacts; identifying relevant stakeholders; defining the goal and scope of an assessment; assessing environmental, economic, and social impacts; evaluating sustainability criteria; developing and evaluating alternatives; and selecting and implementing a decision to support sustainability. Given that the field of nanotechnology is relatively new, there are significant uncertainties regarding its potential human health and ecological risks and impacts. Hence, methods developed to address these uncertainties are also explored. Moreover, since the field of nanotechnology is changing rapidly, this document will be reviewed and updated as additional information becomes available to continue working towards the end goal of sustainability.