This randomized, open-label, two-way crossover study will evaluate the relative bioavailabilty and safety of capecitabine rapid disintegrating tablets (RDT) versus commercial Xeloda tablets in patients with colorectal or breast cancer. Patients will be randomized to a sequence of single oral doses of capecitabine RDT or Xeloda on Days 1 and 2 of a 14-day treatment cycle with Xeloda. Follow-up will be 30 days.

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