The USTUR was expanded in July 1992 through the creation of the National Human Radiobiology Tissue Repository (NHRTR) for radiological specimens. The NHRTR contains frozen tissues, tissue solutions, microscope slides, and paraffin blocks that were collected by the USTUR at autopsy of workers with documented intakes of plutonium, americium, uranium, and thorium. A unique collection of tissues from the Radium Dial Painter program were also received from the Center for Human Radiobiology at the Argonne National Laboratory. The samples in the NHRTR are available to qualified scientists who are interested in conducting studies of localized tissue doses, studies of micro-distribution of the actinide elements, or studies of radiation induced molecular changes.