OUTLINE: This is a multicenter study. Patients, family members, and control individuals complete an extended telephone interview, an extended personal interview, and an epidemiological survey, and contribute a blood specimen. Blood and tumor specimens are examined for the specific pattern of immunohistochemical expression of hMSH2 and HMLH1 to determine the frequency or lack of expression of these two protein products. Patients may be contacted periodically (about every 3 years) to update information about health, health practices, and family history. Patients do not receive the results of the genetic testing and the results do not influence the type or duration of treatment.