['The study was aimed to investigate the relationship between plasma transforming growth factor beta 1 (TGF-β(1)) expression and the characteristics of hepatocellular carcinoma (HCC).', 'Five hundred and seventy-one patients with HCC were subjected. Plasma TGF-β(1) levels were measured by enzyme-linked immunosorbent assay at diagnosis and compared in accordance with clinical and radiological characteristics.', 'Plasma TGF-β(1) levels were significantly higher in the diffuse infiltrative type (n = 159) than in the nodular type of HCC (n = 412; 3.94 ± 0.34 vs. 3.79 ± 0.29 log(10) pg/ml; p < 0.001). They were much higher in patients with portal vein thrombosis or extrahepatic metastasis than in those without (3.88 ± 0.34 vs. 3.81 ± 0.29 log(10) pg/ml, p = 0.008; 3.94 ± 0.35 vs. 3.82 ± 0.30 log(10) pg/ml, p = 0.013, respectively). Also, plasma TGF-β(1) levels showed a positive correlation with the size of HCC (r = 0.014, p < 0.001). Additionally, plasma TGF-β(1) levels were inversely related to the survival periods (p < 0.001).'] Is transforming growth factor beta 1 overexpression closely related to invasiveness of hepatocellular carcinoma?