The emergence of metastatic breast cancer is the most deadly aspect of this disease and once it has spread from the primary site, it is largely incurable. Upon dissemination from the primary tumor, breast cancer cells display preferences for specific metastatic sites. The liver represents the third most frequent site for breast cancer metastasis, following the bone and lung. Despite the evidence that hepatic metastases are associated with poor clinical outcome in breast cancer patients, little is known about the molecular mechanisms governing the spread and growth of breast cancer cells in the liver. In recent years, researchers have utilized animal model systems to isolate breast cancer cells that weakly or aggressively metastasize to the liver and have utilized gene expression profiling to compare these populations. In this manner, genes whose expression is elevated or diminished in highly metastatic breast cancer cells have been identified. We highlight both tumor intrinsic factors as well as aspects of the metastatic microenvironment that contribute to the establishment and growth of breast cancer liver metastases.