Data from a phase I study of the safety and clinical activity of the anti-PD-L1 monoclonal antibody atezolizumab in patients with metastatic renal cell carcinoma (mRCC) indicate that atezolizumab is well tolerated: only 17% of patients had any adverse events, of which, only 4% had immune-mediated events of grade ≤3. No grade 4 or 5 adverse events were reported. 22% of patients had an objective response to treatment, and patients had a median overall survival of 28.9 months. These data indicate a need for further testing of atezolizumab in patients with mRCC.