Inclusion Criteria:

- Adult patients,>/= 18 years of age

- Histological/cytological confirmation of colorectal or breast cancer

- Patient is ambulatory and has a Karnofsky performance status of > 70%

- Body surface area between 1.5 and 2.0 m2

- Either:

- Due to receive Xeloda as monotherapy or as combination therapy as per their treating
physician's treatment plan, or

- Currently receiving Xeloda monotherapy and in the investigator's opinion able to
tolerate study drug dose on Day 1 and Day 2

Exclusion Criteria:

- Any contraindication to Xeloda

- Received Xeloda in the 6 days prior to Day 1

- Subjects with organ allografts (other than autologous bone marrow transplant after
high dose chemotherapy)

- Renal impairment

- Pregnant or lactating females

- Participation in an investigational drug study within 28 days prior to screening

- Lack of physical integrity of the upper gastrointestinal tract, or clinically
significant malabsorption syndrome

- Serious uncontrolled intercurrent infections

- History of clinically significant coronary artery disease

- Concomitant treatment with warfarin

- Known dihydropyrimidine dehydrogenase deficiency