PURPOSE Three new therapies have been approved recently for the adjuvant treatment of stage III melanoma, substantially reducing the risk of tumor recurrences. This study evaluates 3 independent data sets to clarify the survival probabilities of patients with stage III melanoma. PATIENTS AND METHODS The Central Malignant Melanoma Registry (CMMR) evaluated 1,553 patients with a primary diagnosis of stage III melanoma from 2000 to 2012. Studies from the European Organisation for Research and Treatment of Cancer (EORTC), of 573 patients in the observation arm of the 18991 study and 445 patients in the placebo arm of the 18071 study, were evaluated as reference cohorts. The survival outcomes were compared with the published American Joint Committee on Cancer version 8 (AJCCv8) stage III survival data. RESULTS For the CMMR stage III cohort versus the AJCCv8 cohort, the melanoma-specific survival (MSS) rates at 5 years were 67% versus 77%, and at 10 years were 56% versus 69%, respectively. For stage IIIA, the MSS rates at 5 years were 80% versus 93%, and at 10 years were 71% versus 88%; for stage IIIB, the MSS rates at 5 years were 75% versus 83%, and at 10 years were 61% versus 77%. The MSS rates of the EORTC studies either overlapped with or were lower than, the CMMR data. CONCLUSION The MSS rates in the CMMR and EORTC cohorts over the entire stage III are less favorable than those published in AJCCv8. This is particularly true for substages IIIA and IIIB.