Cetuximab, a chimeric monoclonal antibody to epidermal growth factor receptor, is an effective chemotherapeutic agent for patients with metastatic colorectal cancer. Whereas several specific adverse reactions to cetuximab such as skin rash and nail toxicity have been reported, there have been few reports of pneumatosis intestinalis related to cetuximab-containing chemotherapy. We describe here three patients with colorectal cancer who developed pneumatosis intestinalis during treatment with cetuximab-containing chemotherapy, which developed after 7, 19 and 47 weeks of cetuximab treatment, and discovered on routine follow-up computed tomographic scans for response evaluations. None of these patients complained of abdominal pain, showed signs of peritoneal irritation on physical examination or had elevated serum concentrations of acute inflammatory markers. Following cessation of cetuximab and conservative medical treatment, all three patients showed complete resolution of pneumatosis intestinalis on abdominal pelvic computed tomographic scans.