Objective: This study used linked SEER-Medicare data to analyze recent treatment patterns and trends among elderly CRC patients in the US. Methods: Study cohorts included patients aged 65+ newly diagnosed with adenocarcinoma of the colon (CC) or rectum (RC) between 1996 and 2002 (n=60,916) and 1:1 age/sex/location-matched patients from a Medicare 5% sample. Cohorts were followed from index until death or December 31, 2005 to evaluate differences in clinical characteristics, resource use, and initial treatment modalities by cancer site and stage. To analyze trends, a standardized 3-year follow-up was used. Results: Mean (± SD) age among CRC patients and controls was 77 (± 7) years, 46% were male, and 84% were white. About 28% of patients had rectal cancer. Overall, 7% of CRC patients were diagnosed at Stage 0, 24% at Stage 1, 28% at Stage 2, 21% at Stage 3, and 15% at Stage 4 (remainder were unstaged). Between 1996 and 2002, surgery was the primary treatment among CC patients (range: 73-78%), followed by combined surgery/chemotherapy (16-20%), with very little radiation use (<2%). Among RC patients, surgery was the primary treatment (range: 53-56%), followed by surgery/chemoradiotherapy (15-17%), surgery/radiotherapy (8-11%), surgery/chemotherapy (7-9%) and no treatment (7-11%). CRC patients used significantly (P<.001) more health care resources than controls in every category, with the largest differences in use of hospital (23 vs. 12 days), home health (47% vs. 30%) and hospice (24% vs. 9%). Use of all resources remained steady from 1996 to 2002, with slight declines in use of home health (from 47% to 41%; P<.001) and skilled nursing (from a mean of 9 to 8 days; P=.017) and a slight increase in hospice use (from 16% to 19%; P<.001). Conclusion: Treatment patterns and resource use among CRC patients remained steady between 1996 and 2002, and resource use was substantial.