OBJECTIVES: Health state utilities are used in economic modelling to represent the health-related quality of life (HRQL) of patients, with the EQ-5D-3L being the most commonly used tool across disease areas. The objective of this study was to investigate the HRQL of patients with multiple myeloma (MM) across the treatment pathway in a single dataset not limited to one treatment line (as is commonly seen with trial data), and as such, produce an internally consistent set of utility values. METHODS: The EMMOS registry (NCT01241396) full analysis set contains data from 2358 subjects with MM enrolled and followed at 234 sites in 22 countries from 2010 to 2014, including 9080 completed EQ-5D-3L questionnaires. These were scored using the UK algorithm, and analysed using Generalised Estimating Equation techniques. A treatment was considered a new treatment line when a class of treatment (proteasome inhibitor, immunomodulatory agent, chemotherapy) was changed. Stem Cell Transplant [SCT] was also included in the analysis. RESULTS: Patients with newly diagnosed untreated MM have a low utility (approximately 0.46), which increases to approximately 0.60 whilst receiving their first two treatment lines, falling to approximately 0.55 beyond this. The inclusion of prior SCT as a dummy variable increases the explanatory power of the analysis. SCT is associated with a 0.13 increase in utility - even when controlling for the number of prior treatment lines. CONCLUSIONS: This analysis is the most comprehensive available in the disease area, tracking patients through multiple lines of treatment within a single study. The finding that SCT is influential in HRQL (regardless of patient characteristics) should also be factored in to future analyses. The mechanism for this finding however is not clear – it may be that SCT increases HRQL directly, or that only the healthiest patients are able to receive SCT and as such, it represents patient selection.