Background: Adjuvant studies utilizing trastuzumab in early HER2+ breast cancer demonstrated a large reduction in recurrence and death. Post-enrollment central testing showed HER2 non-amplified participants derived similar benefit. Methods: Selection of one of the two chemotherapy regimens is by physician choice: The non-anthracycline regimen is TC (docetaxel 75 mg/m2, cyclophosphamide 600 mg/m2) administered IV every 3 weeks for 6 cycles; the anthracycline regimen is AC followed by WP (doxorubicin 60 mg/m2 and cyclophosphamide 600 mg/m2 administered IV either every 3 weeks or every 2 weeks [per investigator discretion] for 4 cycles followed by paclitaxel 80 mg/m2 IV weekly for 12 doses). Patients are randomly assigned to receive chemotherapy with or without trastuzumab therapy. For patients receiving the TC chemotherapy regimen, trastuzumab is given every 3 weeks during and following chemotherapy until 1 year after the first trastuzumab dose (8 mg/kg loading dose; 6 mg/kg for the remaining doses). For patients receiving the AC followed by WP chemotherapy regimen, trastuzumab begins with the first dose of weekly paclitaxel and will be given weekly for 12 doses (4 mg/kg loading dose; 2 mg/kg for the remaining weekly doses). Following completion of WP, trastuzumab therapy continues with 6 mg/kg doses given every 3 weeks for a total of 1 year. Eligibility: Eligibility includes: node positive or high risk node negative female breast cancer patients; HER2 IHC 1+ or 2+ scores, but non amplified by FISH Statistical Design: The primary aim is to determine whether the addition of trastuzumab to chemotherapy improves invasive disease-free survival (IDFS). 3260 patients will be enrolled to provide statistical power of 0.9 to detect a 33% reduction in the hazard rate of IDFS using a one-sided alpha level of 0.025. Progress: Protocol was activated in January 2011. As of January 27, 2012, 486 of 3260 patients have been enrolled. Supported by NCI U10-12027, -37377, 69651, 69974, and Genentech, Inc.