Background: Adequate lymph node evaluation is required for proper staging of colorectal cancer, and the number of lymph nodes examined is associated with survival. According to current guidelines, the recommended minimum number of lymph nodes examined to ensure adequate sampling is 12. We used data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program to determine the proportion of colorectal cancer patients in the United States who receive adequate lymph node evaluation. Methods: For 116995 adults with colorectal adenocarcinoma, diagnosed from 1988 through 2001, who underwent radical surgery and did not receive neoadjuvant radiation, we evaluated the number of lymph nodes, the likelihood of receiving adequate lymph node evaluation (i.e., at least 12 lymph nodes examined), and the influence of tumor and patient factors on lymph node evaluation. All statistical tests were two-sided. Results: Among all patients, the median number of lymph nodes examined was nine. Only 37% of all patients received adequate lymph node evaluation. The proportion of patients receiving adequate lymph node evaluation increased from 32% in 1988 to 44% in 2001 (Ptrend<.001, Cochran-Armitage test). Advanced tumor stage was statistically significantly associated with adequate lymph node evaluation (odds ratio [OR] of receiving adequate lymph node evaluation = 2.27, 95% confidence interval [CI] = 2.18 to 2.35). Older patients (≥71 years, OR = 0.45, 95% CI = 0.44 to 0.47) were less likely to receive adequate lymph node evaluation than younger patients, and those with left-sided (OR = 0.45, 95 % CI = 0.44 to 0.47) or rectal (OR = 0.52, 95% CI = 0.50 to 0.54) cancers were less likely to receive adequate lymph node evaluation than patients with right-sided cancers. In all analyses, geographic location was an important predictor of adequate lymph node evaluation, which ranged from 33% to 53%, depending on geographic location. Conclusions: In 2001, the majority of patients with colorectal cancer still received inadequate lymph node evaluation. The association of demographic variables, particularly patient age and geographic location, with adequate lymph node evaluation indicates that local surgical and pathology practice patterns may affect adequacy of lymph node evaluation.