Eighteen of 78 patients (23%) with metastatic colorectal cancer developed clinically significant metastases to the central nervous system (CNS). The patients developing CNS metastases had a decreased likelihood of associated liver metastases compared to the patients without CNS metastases (22% versus 80%). Pulmonary metastases were present in 55% of patients with CNS lesions and in 25% of those without CNS lesions. Overall survival from diagnosis of the primary tumor was comparable (median, 28 months) for patients with or without CNS lesions. The incidence of CNS metastases was comparable irrespective of Duke stage at presentation. For early lesions (Duke B or C), CNS metastases were associated with a shorter survival (31 versus 42 months). For advanced disease (Duke D lesions) at presentation, the overall survival of the group with CNS metastases was longer (24 versus nine months). Therefore, the longer survivorship of patients with advanced disease may contribute to a greater likelihood of CNS metastases.