Over the last decade, regulators have accelerated their focus on vapor intrusion risk at hazardous cleanup sites. This has led to new cleanup standards, policies and guidance to evaluate potential risks, environmental investigation requirements for brownfield redevelopments, and the reopening of previously closed remedial actions. Recently, attention has turned from chronic to acute vapor intrusion risk. Although protection of human health is paramount, this recent focus has been plagued with concerns about the validity of the underlying science and a lack of comprehensive guidance from regulators on how to respond. This article explores the evolution of vapor intrusion regulation, particularly developments addressing acute risk, as well as trends in vapor intrusion- related litigation.