Tyrosine kinase inhibitors are de facto the more used targeted therapies for upfront treatment of metastatic renal cell carcinoma (mRCC). Among these, sunitinib and pazopanib have reported greater activity in term of progression-free survival and overall survival compared with interferon-α or placebo in two independent large phase III studies. Despite a large use in clinical practice these molecules had never been compared. The COMPARZ study recently published in the New England Journal of Medicine reports the results of a non-inferiority trial that comparing pazopanib to sunitinib as first line of therapy in mRCC patients. Here we report the activity and safety data of the study and we discuss several critical aspects related to the study design and possible confounding factors that may alter the results’ interpretation.