This study will evaluate the efficacy and safety of pazopanib compared to sunitinib in subjects with advanced RCC who have received no prior systemic therapy for advanced or metastatic RCC. Subjects will be randomized in a 1:1 ratio to receive either 800mg pazopanib to be administered once daily orally continuous dosing or 50mg sunitinib to be administered in 6-week cycles: 50mg orally daily for 4 weeks followed by 2 weeks off treatment. Subjects are permitted to receive supportive care throughout the study including transfusion of blood and blood products, treatment with antibiotics, anti-emetics, anti-diarrheal agents, analgesics, erythropoietin, or bisphosphonates, when appropriate. The study treatment will continue until subjects experience disease progression, unacceptable toxicity, withdraw consent, or death.