['High dose melphalan (HDM) and autologous stem cell transplantation (ASCT) retains a central role in the treatment of myeloma. The aim of this study was to determine whether HDM exposure (area under the concentration vs. time curve, AUC), is significantly associated with transplant outcomes.', 'Melphalan concentrations were measured in six to 11 plasma samples collected after HDM (median 192\xa0mg\xa0m(-) (2) ) to determine melphalan AUC for a total of 114 patients. Binary logistic regression was used to assess whether melphalan AUC was associated with severe (≥ grade 3) oral mucositis. Multivariate Cox regression was used to assess whether melphalan AUC was significantly associated with time to progression, progression-free survival and overall survival (OS).', 'Melphalan AUC ranged from 4.9 to 24.6\xa0mg\xa0l(-1) \xa0h, median 12.84\xa0mg\xa0l(-1) h. Melphalan AUC above the median was a risk factor for severe mucositis (HR 1.21, 95% CI 1.06, 1.38, P\xa0=\xa00.004) but was also associated with significantly improved overall survival (OS) (HR 0.40, 95% CI 0.20, 0.81, P\xa0=\xa00.001), with an estimated median survival of 8.50\xa0years vs. 5.38\xa0years for high vs. low AUC groups. Multivariate analysis did not identify melphalan AUC as being significantly associated with time to progression or progression-free survival.'] Is high melphalan exposure associated with improved overall survival in myeloma patients receiving high dose melphalan and autologous transplantation?