14578 Background: Bevacizumab (Avastin) is a recombinant humanized monoclonal antibody to vascular endothelial growth factor (VEGF) that functions as an anti-angiogenic agent. VEGF is a glycoprotein, important for regulation of angiogenesis in normal and pathologic cells and is required for the maintenance of immature blood vessels, found in tumors. In addition to direct antiangiogenic effects, bevacizumab improves chemotherapy delivery by altering tumor vasculature as well as decreasing the size and number of liver tumors in mouse xenograft model of human colon cancer metastases. This study aimed to look for predictors of the development of major toxicities such as bleeding and clotting that would increase the incidence of such events in patients with metastatic colorectal carcinoma on Bevacizumab therapy. Methods: The study was a retrospective analysis over the past 2 years, reviewing the charts of 59 successive patients receiving bevacizumab in our institution. Particular emphasis was placed on age, gender, tumor type and location, location of metastases, chemotherapy regiment/number of cycles, past medical history, hemoglobin/hematocrit values, PT/INR values, liver function tests and albumin values at the time of the diagnosis and event. Utilizing univariant and multivariant analysis the goal was to determine contributing risk factors for increased incidence of bleeding and clotting. Results: 20.3% of the patients were found to have a major complication, such as clotting or bleeding. Once analyzed, there were four statistically significant indicators (p < 0.05) that predicted for the incidence of either one of the events. They included older patient age, low albumin values at the time of the event (as defined by the institution value of less than 3.6), location of the tumor (cecum, ascending colon and sigmoid colon were predominant), and the site of the metastasis (liver and lung). Conclusions: Clotting and bleeding complications in patients on Bevacizumab are not uncommon. It is clear that age, low albumin values, metastatic site and tumor location contribute to an increased incidence of such events in patients with metastatic colon cancer on Bevacizumab therapy. [Table: see text]