Forty years ago this year, smoldering multiple myeloma was defined as a clinical entity that identifies a group of patients with a substantial burden of disease but with a relatively indolent natural history compared with symptomatic disease. Since then, there has been a revolution in the therapeutic options for multiple myeloma. The aim of this article is to describe recent advances in the identification of those patients who are at the highest risk of progression and whether they may benefit from therapy. Treatment of smoldering myeloma is an area of active debate and we present contrasting interpretations of the available trial data. We conclude by identifying the priorities for research that will help to clarify the management of this condition, which can be challenging for physicians and patients alike.