['To improve colorectal cancer outcomes, appropriate adjuvant therapy (chemotherapy, radiation therapy) should be given. Numerous studies have demonstrated underuse of adjuvant therapy in colorectal cancer. The current study examines variables associated with underuse of adjuvant therapy.', 'Three population-based databases were linked: California Cancer Registry, California Patient Discharge Database, 2000 Census. All colorectal cancer patients diagnosed from 1994 to 2001 were studied. Patient characteristics (age, gender, race/ethnicity, comorbidities, payer, diagnosis year, socioeconomic status) were used in five multivariate regression analyses to predict receipt of chemotherapy for Stage III colon cancer, and receipt of chemotherapy and radiation therapy for Stages II, III rectal cancer.', 'The overall cohort was 18,649 Stage III colon cancer and Stages II, III rectal cancer patients. Mean age was 68.9 years, 50 percent male, 74 percent non-Hispanic white, 6 percent black, 11 percent Hispanic, 9 percent Asian, and 65 percent had no significant comorbid disease. Receipt of chemotherapy was 48 percent for Stage III colon cancer, 48 percent for Stage II rectal cancer, and 66 percent for Stage III rectal cancer. Receipt of radiation therapy was 52 percent for Stage II rectal cancer and 66 percent for Stage III rectal cancer. In all five models, low socioeconomic status predicted underuse of chemotherapy or radiation therapy (P < 0.016). Race/ethnicity was not statistically associated with underuse in any of the models.'] Does a patient 's race/ethnicity explain the underuse of appropriate adjuvant therapy in colorectal cancer?