Background/Aim: To evaluate the effectiveness and safety of nivolumab plus ipilimumab for untreated metastatic renal cell carcinoma in real-world clinical practice in Japan based on 1-year follow-up results. Patients and Methods: This multicentre, retrospective study analysed 45 metastatic renal cell carcinoma patients who received nivolumab plus ipilimumab between August 2018 and January 2019 in Japan. Data were extracted from patients' medical records. Subgroup analyses were performed based on baseline demographic data and treatment history. Results: The objective response rate was 42.5% (complete response rate: 10.0%). The 12-month overall survival rate was 81.4% and the progression-free survival rate was 56.1%. Thirty-five patients (77.8%) showed any grade treatment-related adverse events and 17 (37.8%) showed grade ≥3 treatmentrelated adverse events, with no significant difference in safety between subgroups. Conclusion: The effectiveness and safety of nivolumab plus ipilimumab in real-world clinical practice with 1-year follow-up were comparable with those of the CheckMate 214 trial.Based on GLOBOCAN's 2018 data, renal cell carcinoma (RCC) accounts for approximately 2% of global cancer diagnoses (1, 2). In Japan, the crude incidence rates of RCC in men and women were 8.2 and 3.5 per 100,000, respectively (3). Survival of patients with RCC is highly dependent on the stage at diagnosis, with a 5-year relative survival rate of 93% for stage I localised RCC, 72.5% for stage II/III regional RCC and only 12% for stage IV metastatic RCC (mRCC) (2). In the past two decades, treatments targeting vascular endothelial growth factor receptor tyrosine kinase and mammalian target of rapamycin (mTOR) pathways have clearly improved mRCC management (4). In Japan, tyrosine kinase inhibitors (TKIs) were the most common first-line treatment (72.2%) in patients with mRCC, followed by mTOR inhibitors (14.3%) and cytokines (13.5%), from 2012 to 2015 (5). However, TKIs and mTOR inhibitors are associated with inherent resistance and show limited overall survival.Recently, the focus of mRCC treatment research has moved to immuno-oncology, and evaluations of immune checkpoint inhibitors have shifted the treatment paradigm of mRCC (4). A randomised phase III clinical trial, CheckMate 214, has demonstrated that nivolumab plus ipilimumab combination therapy was superior to a TKI, sunitinib, with respect to therapeutic effects in patients with 6199 This article is freely accessible online.