3545 Background: We targeted the VEGF pathway in a phase I trial combining bevacizumab, a monoclonal antibody to VEGF, with sorafenib, a multikinase inhibitor of VEGF-receptor-2 and Raf-kinase. We hypothesized that the combination would result in suppression of angiogenesis and tumor growth. Methods: Eligible patients had advanced solid tumors, ECOG 0–1, good organ function, and no prior treatment with either agent. Sorafenib 200 mg BID and bevacizumab 5 mg/kg q2wks every 28d was the MTD on which 28 pts were enrolled. Patients were randomized to receive single agent sorafenib or bevacizumab for one cycle followed by combination therapy with both agents thereafter. Serum for VEGF, IL-6, and IL-8 analysis was drawn on-study and then monthly. Angiogenic potential of patient sera was measured using rat aortic ring assay (RARA) with pre-treatment and cycle 4 sera. A Wilcoxan rank sum test was used to evaluate the difference between values at the indicated time points. Plasma for pharmacokinetics (PKs) was draw...