Bevacizumab, a humanized monoclonal antibody against vascular endothelial factor (VEGF), is approved for the treatment of metastatic colon cancer, but it has also shown efficacy in first line therapy of non-squamous-cell non-smallcell lung cancer, breast cancer and clear-cell renal cancer. Antiangiogenic therapy severe toxic effects such as stroke, myocardial infraction, angina, arterial thromboembolism, pulmonary embolism or haemorrhage, gastrointestinal perforation, heart failure should be taken into account during treatment with bevacizumab. We describe and discuss two cases of cancer patients who developed fatal arterial thromboembolic episodes after administration of bevacizumab. Due to the recent launch of antiangiogenic agents and the limited experience with their use in clinical practice, their adverse effects and pharmacological toxicities, sometimes fatal, are not well-established and a detailed registration of them is needed.