GRIM-19 (gene associated with retinoid-interferon-induced-mortality 19) is a newly discovered cell death regulator. This paper overviews its functions in oncogenesis and other diseases and associated mechanisms, and the text covers the cellular location of GRIM-19 and its function in cell apoptosis and respiratory chain maintenance, as well as its relations with viral and bacterial infections, and with oncogenesis of a variety of malignant tumors.