Inclusion Criteria:

- Signed informed consent

- Available tissue for central laboratory evaluation of HER2 status

- Histologically confirmed, measurable or nonmeasurable but evaluable, HER2 positive
metastatic breast cancer (HER2 positive is defined as 3+ staining by IHC or gene
amplification by FISH, determined by the local or central laboratory)

- Life expectancy >6 months

- Female, age >=18 years

- ECOG performance status of 0, 1, or 2

- Adequate bone marrow function as indicated by the following: *ANC >1500/uL, *Platelet
count >=100,000/uL

- Adequate renal function, as indicated by creatinine <=1.5× upper limit of normal
(ULN)

- Adequate liver function, as indicated by bilirubin <=1.5× ULN and AST or ALT <2× ULN
unless related to primary disease

- Use of an adequate means of birth control (women of childbearing potential)

Exclusion Criteria:

- Initiation of Herceptin >=4 weeks after beginning taxane chemotherapy

- Prior chemotherapy for metastatic disease

- Prior cumulative anthracycline dose of >360 mg/m2

- History of significant cardiac disease or uncontrolled arrhythmias

- Ejection fraction of <50% or below the lower limit of normal

- Active infection

- Symptomatic or untreated brain metastases

- Pregnancy or lactation

- Concomitant malignancies or previous malignancies within the last 5 years, with the
exception of adequately treated basal or squamous cell carcinoma of the skin or
carcinoma in situ of the cervix

- Symptomatic intrinsic lung disease or extensive tumor involvement of the lungs,
resulting in dyspnea at rest

- Hypersensitivity to study medications

- Major organ failure or systemic disease precluding the safe administration of study
medications