Aim: Colorectal cancer patients are treated with surgery and sometimes radiotherapy and chemotherapy. Transforming growth factor beta-1 (TGF-β1) acts both as an inhibitor of tumor growth and as a promoter of tumor progression. The aim of this study was to determine the levels of TGF-β1 in plasma in colorectal cancer patients and relate these to the effect of clinicopathological variables. Method: One hundred patients scheduled for colorectal cancer surgery were included. Blood samples were taken during surgery and later assayed with enzyme linked immunsorbent assay for total TGF-β1 and active TGF-β1. Result: Total and active TGF-β1 was higher in tumor samples compared to controls (p<0.001).Total TGF-β1 was higher in patients with metastases compared to patients without. Active TGF-β1 levels were not found statistically different in patients with metastases.. Conclusion: Higher levels of total TGF-β1 in plasma at surgery may be indicate of distant metastases, Measurement of total TGF-β1 in colorectal cancer patients may be of clinical use in the future.