Background: Pazopanib is an oral, selective, multikinase inhibitor of VEGF receptors 1/2/3, PDGF receptors α/ß, and stem cell factor receptor (c-Kit) that is approved for first-line treatment of patients with advanced renal cell carcinoma (RCC) and for patients who received prior cytokine therapy. The COMPARZ study of pazopanib versus sunitinib as first-line treatment demonstrated noninferiority of pazopanib for progression-free survival (PFS) in the intention-to-treat population, and pazopanib statistically favored health-related quality of life (HRQoL) in 11 of the 14 domains measured (NEJM 2013;369:722-31). The PISCES patient preference study demonstrated that significantly more patients preferred pazopanib over sunitinib due to overall better HRQoL and less fatigue (JCO 2012;30 suppl 15:CRA4502). The purpose of the PRINCIPAL study is to evaluate the real-world effectiveness and safety of pazopanib in patients with advanced or mRCC. Methods: This is a global, multicenter, prospective, observational study (VEG115232, NCT01649778) designed to enrol up to 700 patients. Primary endpoints include PFS, overall response rate, overall survival, relative dose intensity data, HRQoL data, and safety data. Additional treatment strategies for RCC will be obtained post-progression. Key inclusion criteria include a clinical decision to initiate treatment with pazopanib (before enrolment in the study), no prior systemic therapy for advanced or mRCC, and no participation in an interventional trial. The study has enroled 339 patients to date and is currently recruiting in 15 countries, including Europe, Asia, Latin America, and the United States. This study will determine patient outcomes with pazopanib in a real-world setting in terms of efficacy, safety, and patient compliance outside the normal parameters of a controlled trial. PRINCIPAL will also provide further data in patient groups that were under-represented in the controlled clinical trials to date, such as the elderly and patients with co-morbidities. Clinical trial information: NCT01649778.