Background: \- Gastrointestinal cancers can occur in the throat, stomach, gallbladder, liver, pancreas, and colon. Researchers are interested in evaluating how active the immune system is in trying to fight the cancer by studying blood and tumor tissue donated from individuals who have been diagnosed with gastrointestinal cancers.

Objectives: \- To collect blood and tumor samples from individuals who have been diagnosed with gastrointestinal cancers in order to study the immune system s response to the cancer.

Eligibility: \- Individuals at least 18 years of age who have been diagnosed with throat, stomach, gallbladder, liver, pancreatic, or colon cancer, and are scheduled to be treated at the National Institutes of Health.

Design: * The study will require at least one but no more than four visits to the National Institutes of Health Clinical Center. * Participants will be screened with a physical examination and medical history, and will provide a baseline blood sample for study. * Participants will provide additional blood samples 2 and 4 months after the baseline sample, as well as a final sample at the completion of the treatment protocol. * Participants will provide tumor tissue samples only if they undergo a surgical procedure related to the treatment for their gastrointestinal cancer. * No treatment will be provided as part of this protocol.