Annie Cowan, BA, Dana-Farber Cancer Institute, Boston, MA, discusses the two major classes of precursor multiple myeloma states: monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma. Ms Cowan then further explains these two precursor states, and how they are differentiated from one another based on levels of M proteins and percentage of bone marrow plasma cells. This interview took place at the American Association for Cancer Research Annual Meeting in New Orleans, LA.