Context: A 1990 National Institutes of Health Consensus Conference recommended that patients with stage III colon cancer receive adjuvant chemotherapy because survival was improved in clinical trials in patients who received a 5-fluorouracil-based regimen. Objective: To determine whether adjuvant chemotherapy is used in the community as a standard of practice that improves outcome and whether it failed to benefit any specific sets of patients. Design, Setting, and Participants: Prospective data from 85 934 patients with stage III colon cancer from 560 hospital cancer registries were entered into the National Cancer Data Base between 1990 and 2002 and included standard clinical, pathological, and first course of treatment variables. Main Outcome Measures: Prevalence of adjuvant chemotherapy usage and 5-year survival in patients treated in US hospitals. Results: Adjuvant chemotherapy use increased from 39%in 1991 to 64%in 2002 but was lower in black, female, and elderly patients. It improved 5-year survival from almost 8%in 1991 to more than 16%in 1997 compared with surgery alone. Adjuvant chemotherapy increases survival in elderly patients as much as it does in younger patients. However, the benefit of adjuvant chemotherapy in blacks and those with hi gh-grade cancers is not as great. Conclusions: Adjuvant chemotherapy use has in creased from 1990 to 2002 for patients with stage III colon cancer with an assoc iated increase in 5-year survival of 16%. The benefit of adjuvant chemotherapy seems to be lower in black patients and highgrade cancers. Women have the same benefit but are less often treated. Elderly patients have the same benefit as yo unger patients but are less frequently treated. New options for adjuvant therapy in 2004-2005 may further improve the outcome of patients with stage III colon cancer. Context: A 1990 National Institutes of Health Consensus Conference Conference that recommends that patients with stage III colon cancer receive adjuvant chemotherapy because survival was improved in clinical trials in patients who received a 5-fluorouracil-based regimen. Objective: To determine whether adjuvant chemotherapy is used in the community as a standard of practice that improves outcome and whether it failed to benefit any specific sets of patients. Design, Setting, and Participants: Prospective data from 85 934 patients with stage III colon cancer from 560 hospital cancer regstries entered into the National Cancer Data Base between 1990 and 2002 and included standard clinical, pathological, and first course of treatment variables. Main Outcome Measures: Prevalence of adjuvant chemotherapy usage and 5-year survival in patients treated in US hospitals. Results: Adjuvant chemotherapy use increased from 39 % in 1991 to 64% in 2002 but was lower in black, female, and elderly patients. It impr oved 5-year survival from almost 8% in 1991 to more than 16% in 1997 compared with surgery alone. Adjuvant chemotherapy increases survival in elderly patients as much as it does in younger patients. However, the benefit of adjuvant chemotherapy in blacks and those with hi gh-grade cancers is not as great. Conclusions: Adjuvant chemotherapy use has in creased from 1990 to 2002 for patients with stage III colon cancer with an assoc iated increase in 5-year survival of 16%. The benefit of adjuvant 10 Women have the same benefit but are less often treated. Elderly patients have the same benefit as yo unger patients but are less frequently treated. New options for adjuvant therapy in 2004-2005 may further improve the outcome of patients with stage III colon cancer.