Bevacizumab, a humanized monoclonal antibody used to treat recurrent and metastatic colorectal cancer, targets the vascular endothelial growth factor (VEGF) molecule. It is hypothesized that bevacizumab works by both depriving tumors of the neovascularity they require to grow, and by improving local delivery of chemotherapy through alterations of tumor vasculature permeability and Starling forces. Complications of bevacizumab treatment include bowel ischemia and perforation, but to date, these complications have only rarely been described as occurring at the site of presumably healed anastomoses following surgery. We report two cases of delayed, “spontaneous” low anterior colorectal anastomotic dehiscence and one right colon anastomotic colocutaneous fistula associated with bevacizumab therapy. After seeing three patients with complications arising from apparently healed low anterior colorectal or right colon anastomoses following initiation of bevacizumab therapy for treatment of metastatic colorectal cancer, we reviewed the experience of The Cancer Institute of New Jersey (CINJ) with use of bevacizumab in approximately 50 patients between April 2004 and December 2006. The three index cases had been treated surgically at CINJ but received chemotherapy elsewhere. None of the 50 patients receiving bevacizumab at CINJ who had previous colon or rectal anastomoses were identified as having this complication. The medical records of the three index cases were reviewed and analyzed. Additionally, a Medline search was performed to identify other reports documenting similar cases. Two reports of related cases were found in the literature. In two of our index cases who underwent low anterior anastomoses, the patients had received preoperative pelvic irradiation before their initial low anterior resection. In one of the two cases, the initial resection was complicated by an anastomotic leak requiring proximal diversion and then subsequent stoma takedown. In both cases, the dehiscence occurred more than 1 year after anastomosis, and became evident 1–10 months following initiation of bevacizumab treatment. In the third index case, a colocutaneous fistula arising from the anastomotic site presented 5 months following right colon resection and 3 months after starting adjuvant systemic therapy with FOLFOX (5-fluorouracil (5-FU), leucovorin, and oxaliplatin) and bevacizumab. Delayed colorectal anastomotic complications may occur in association with bevacizumab therapy. Contributing factors may include anastomotic leak at the time of the original operation and history of anastomotic irradiation. Clinicians treating patients who receive bevacizumab following colectomy for colorectal cancer should be aware of this possible life-threatening complication. These findings may also be relevant to the design of trials of the use of bevacizumab for the postoperative adjuvant treatment of patients with colorectal cancer. J. Surg. Oncol. 2008;97:180–185. © 2007 Wiley-Liss, Inc.