The objective of the NIMH Toxicological Evaluation of Novel Ligands program is to advance the discovery of biomarkers by accelerating the development and application of novel ligands for PET, SPECT, and MRI imaging in humans by providing toxicology and safety assessment of promising, target-selective compounds. The program also provides limited assessment of novel psychoactive agents for clinical research and as potential therapeutics. Toxicology and safety data generated by the program are used to support Investigational New Drug (IND) applications to the Food and Drug Administration (FDA) by investigators, or for Radioactive Drug Research Committee (RDRC) evaluation of a compound for human studies. The program will also provide access to toxicology consultation services and support for initial in vitro and early stage in vivo toxicity testing for promising lead compounds from NIMH-relevant ligand and therapeutics development projects.