Inclusion Criteria:

- Adult female patients, >/= 18 years of age

- Cytolologic/histopathologic confirmed diagnosis of metastatic breast cancer

- Prescribed Xeloda as in routine clinical practice

- Informed consent signed

Exclusion Criteria:

- Participation in any other clinical trial

- History of severe and unexpected reactions to fluoropyrimidine therapy

- Hypersensitivity to capecitabine or to any of the excipients of fluorouracil

- Known dihydropyrimidine dehydrogenase (DPD) deficiency

- Pregnant or lactating women

- Severe leucopenia, neutropenia, or thrombocytopenia

- Severe hepatic impairment

- Severe renal impairment (creatinine clearance below 30 ml/min)

- Treatment with sorivudine or its chemically related analogues, such as brivudine

- Refusal to give consent