Abstract Transforming growth factor-β1 (TGF-β1) has been implicated in tumor progression by promoting angiogenesis or suppressing immune system. We reported previously that transforming growth factor-β1 (TGF-β1) is overproduced by human hepatocellular carcinoma (HCC) tissues and that plasma TGF-β1 levels are elevated in patients with HCC. In the present study, we investigated the relationship between plasma TGF-β1 levels and tumor vascularity as assessed by conventional celiac angiography in 17 patients with HCC. The plasma TGF-β1 level did not correlate with tumor size or underlying liver disease. However, we found that plasma TGF-β1 levels correlated positively with the tumor vascularity. These results suggest that excessive TGF-β1 production may contribute to tumor angiogenesis in HCC.