This 2 arm study will compare the efficacy and safety of Avastin plus Herceptin/docetaxel, versus Herceptin/docetaxel alone, in patients with HER2 positive locally recurrent or metastatic breast cancer who have not received prior chemotherapy for their metastatic disease. Patients will be randomized 1:1 to receive either Avastin (15mg/kg iv q3weeks) + Herceptin (8mg/kg iv loading dose and 6mg/kg iv q3weeks maintenance) + docetaxel (100mg/m2 iv q3weeks) or Herceptin + docetaxel alone. The anticipated time on study treatment is until disease progression, and the target sample size is 100-500 individuals.