This paper describes the development of the Functional Assessment of Cancer Therapy-Colorectal (FACT-C)--a questionnaire assessing quality of life concerns pertinent to colorectal cancer patients. This self-report instrument combines specific concerns related to colorectal cancer with concerns that are common to all cancer patients as assessed with the FACT-General (FACT-G). Three separate and distinct validation samples were used with different ethnic and stage of disease compositions. Results suggest that the FACT-C is a reliable and valid measure in both its English and Spanish language versions. Specifically, the FACT-C evidenced good internal consistency reliability and concurrent validity, as well as an ability to distinguish between groups based on functional status and extent of disease. The FACT-C was also found to be sensitive to changes in functional status. Colorectal cancer-specific items form the Colorectal Cancer Subscale (CCS) which was found to have adequate convergent and divergent validity. Internal consistency was adequate in most samples. In addition, the CCS was able to distinguish among groups that differed in functional status and was sensitive to change in functional status. It is recommended that the entire FACT-C (rather than simply the CCS) be used when studying patients with colorectal cancer in order to provide a comprehensive assessment of quality of life. Recommendations are offered concerning the appropriate use of these measures in clinical research and directions for future research with colorectal cancer patients.