With the passing of Dr. Gilman D. Veith on August 18, 2013, the research community lost one of its true visionaries in the development and implementation of alternative in silico and in vitro toxicology models in human health and ecological risk assessment. His career spanned more than four decades, during which he repeatedly demonstrated vision and leadership to advance alternative testing and assessment research and to guide the adoption of research accomplishments into U.S. and international chemical regulatory programs. His ability to advance toxicological and environmental exposure research, and associated quantitative structure– activity relationships (QSARs), for application in environmental regulatory decision making was achieved by a focus on establishing a transparent, mechanistic understanding of the chemistry and biology underlying alternative experimental and mathematical models. Dr. Veith was a pioneer of the application of alternative methods, especially QSAR to industrial chemicals, which traditionally lacked the experimental data already available for pesticides and pharmaceuticals. His lifelong vision and leadership were recognized by a number of awards, including the Henry J. Heimlich, M.D., Award for Innovative Medicine in 2010. Through Dr. Veith’s accomplishments, the use of alternative approaches in toxicity testing and risk assessment was implemented in the 20th century. His leadership also provided the scientific and regulatory framework for developing and applying in vitro and in silico techniques in what is now coined as 21stcentury toxicology.