The interagency agreement between NIEHS and NCGC/ NCATS is intended to support on-going and anticipated studies to be conducted by NCGC/ NCATS using high throughput screening (HTS) assays as a part of the NTP HTS Initiative (Tox21). Batteries of HTS assays have been identified that should allow substances that lack needed toxicological data to be prioritized for further investigation and for generation of data to support the development of predictive models for in vivo biological response. Current efforts are concentrating on assays that measure nuclear receptor activity (both agonism and antagonism) and cellular stress responses following compound exposure. Ultimately, the use of HTS assays will greatly increase testing throughput and decrease the cost of testing uncharacterized compounds for toxicological potential.