The values of ornithine decarboxylase (ODC) activity in hepatic and extrahepatic metastases from primary colorectal cancer were studied. Adjacent noninvolved tissue was used as a control. Liver metastases had significant elevated ODC levels over surrounding liver (0.271 vs. 0.065, respectively, P less than .008). Results similar to those found in liver metastases were noted in extrahepatic metastases (median value, 0.271). This study discusses the possible reasons for these elevations and emphasizes that these differences may have potential roles in the areas of diagnosis, staging, monitoring of the disease, and therapeutic interventions in colorectal cancer and its hepatic and extrahepatic metastases.