A new article from authors in the Center of Excellence for 21st Century Toxicology describes a framework to systematically and quantitatively integrate mechanistic data in assessments of potential carcinogenicity. The framework builds on the key characteristics organizational approach that is being implemented by authoritative bodies globally, by accounting for the quality and relevance of individual studies when developing weight-of-evidence conclusions regarding the activity of key characteristics. The proposed framework provides a flexible solution to quantitively integrate all available data in a systematic and transparent manner that accords greater weight to data that are best suited to the assessment of potential human carcinogenicity. The paper by Dr. Daniele Wikoff and colleagues has been accepted for publication in Toxicological Sciences and is on the 21CT website.