To study the blood flow in normal liver tissue and in liver malignancies after occlusion of the hepatic artery or the portal vein, an adenocarcinoma was inoculated in the left liver lobe of 10 rats. Eight days postoperatively, blood flow in normal hepatic tissue and tumour was estimated by laser Doppler flowmetry (LDF). In both normal tissue and tumour, occlusion of the hepatic artery reduced LDF values by approximately 30%, whereas occlusion of the portal vein reduced LDF values by approximately 70%. These findings indicate that changes of hepatic blood flow can be monitored by LDF, and that the portal blood flow is dominating also in liver metastasis.