Background & Aims: The potential presence of lymph node metastases in patients with colorectal cancer (CRC) limits the application of minimally invasive techniques of resection. We used data from the National Cancer Institute's Surveillance, Epidemiology, and End Results registry to better understand the underlying risk of lymph node metastases and factors that influence this risk in a population-based fashion. Methods: In a cohort of 124,180 CRC patients diagnosed from 1988 through 2002 treated with radical surgery without neoadjuvant irradiation, we assessed the proportion of patients who were lymph node positive and determined factors that influenced the risk of lymph node metastases including patient characteristics, anatomic location, and histopathologic factors. Results: Among all patients, the proportion of lymph node metastases was 34.5%. The overall proportion of node positivity was 8% for T1 tumors, 18.5% for T2 tumors, 42% for T3 tumors, and 50% for T4 tumors. Nodal metastases were noted in 7% of proximal T1 colon tumors, 7.5% of distal T1 colon tumors, and 10.1% of T1 rectal tumors. Patients with poorly differentiated tumors were much more likely to be node positive (52%) than patients with well-differentiated tumors (20%) (P < .0001). Conclusions: Even patients with superficial CRCs have a significant risk of nodal metastases. This risk should be considered when balancing the risks and benefits of minimally invasive techniques such as local excision or endoscopic resection for the treatment of CRC.