Auranofin, a reprofiled FDA-approved drug originally designed to treat rheumatoid arthritis, has emerged as a promising anti-parasitic drug. It induces the accumulation of reactive oxygen species (ROS) in parasites such as Toxoplasma gondii, the pathogen causing Toxoplasmosis. We generated auranofin resistant T. gondii mutant lines through chemical mutagenesis in order to identify the molecular target of this drug, or other proteins involved in the molecular pathway of auranofin function. Specifically, genetic mutations in the auranofin resistant mutant lines could identify mutated genes that confer auranofin resistance or affect the redox homeostasis in parasites.