A toluidine derivative and a nonsteroidal antiandrogen that is structurally related to bicalutamide and nilutamide. Flutamide and its more potent active metabolite 2-hydroxyflutamide competitively block dihydrotestosterone binding at androgen receptors, forming inactive complexes which cannot translocate into the cell nucleus. Formation of inactive receptors inhibits androgen-dependent DNA and protein synthesis, resulting in tumor cell growth arrest or transient tumor regression. (NCI04)