Pharmacokinetics and metabolism of droloxifene, a new antiestrogenic drug, have been investigated by single- and multiple-dose studies in postmenopausal patients with advanced breast cancer. Short terminal elimination half-life, low accumulation, and improved drug tolerability are the most striking features of this safe and effective new antiestrogen. Bioequivalence of film-coated tablet, tablet, and standard solution of droloxifene has been shown. The concentrations of droloxifene and its metabolites have been determined by a highly selective HPLC method.