This single arm study will evaluate the efficacy and safety of a first-line regimen of Avastin and XELOX (oxaliplatin + Xeloda) in patients with metastatic cancer of the colon or rectum. Patients will receive 21-day cycles of treatment, comprising Avastin 7.5mg/kg iv on day 1, oxaliplatin 130mg/m2 iv on day 1, and Xeloda 1000mg/m2 po twice daily on days 1-14, for a maximum of 6 months. Patients with stable disease or complete or partial response may continue on Avastin therapy. The anticipated time on study treatment is until disease progression, and the target sample size is 100-500 individuals.