The CONTAIN code is the U.S. Nuclear Regulatory Commission ’s best-estimate code for the evaluation of the conditions that may exist inside a reactor containment building during a severe accident. Included in the phenomena modeled are thermal hydraulics, radiant and convective heat transfer, aerosol loading and transient response, fission product transport and heating effects, and interactions of coolant and corium with the containment atmosphere and structures. An enhanced version of the code, designated CONTAIN LMR, has been used by groups in Japan and the Federal Republic of Germany to assess the ability of CONTAIN to analyze accident consequences for liquidmetal reactor (LMR) plants. Collaborative efforts to improve the modeling capabilities of CONTAIN for LMR applications have also been pursued. A brief description of physical models is presented, followed by a short review of validation exercises performed with CONTAIN. Finally, some demonstration calculations of an integrated LMR application are presented.