Thioredoxins are involved in various biochemical systems and mediate both redox and nonredox functions. In mammalian cells, thioredoxin functions as an endogenous glucocorticoid receptor activating factor and as an adult T-cell leukemia-derived factor (ADF) that stimulates expression of interleukin-2 receptor in human T-cell leukemia virus (HTLV)-I transformed T cells. We have mapped the thioredoxin gene (Txn) and its processed pseudogene (Txn-ps1) in the mouse using a panel of interspecific backcross mice. Txn maps to Chr 4, whereas Txn-ps1 maps to the proximal region of Chr 1.