It is known that angiogenesis plays an important role in the growth and metastasis of solid tumours. Several angiogenic factors have been identified and platelet-derived endothelial cell growth factor (PD-ECGF) is thought to be one such factor. Recently, it was reported that thymidine phosphorylase (dThdPase) is identical to PD-ECGF. Using immunohistochemical staining with an anti-dThdPase antibody, we investigated the correlation between dThdPase expression and the microvessel density in 120 gastric carcinomas. The microvessel density, determined by immunostaining for factor VIII-related antigen, was significantly higher in dThdPase-positive tumours than in dThdPase-negative tumors. There was a significant correlation between dThdPase expression and the increment of microvessel density. Moreover, regarding distant organ metastasis, the frequency of hepatic metastasis was significantly higher (P < 0.01) in patients with dThdPase-positive tumours than in those with dThdPase-negative tumors. In summary, it was suggested that dThdPase expression is closely associated with the promotion of angiogenesis and hepatic metastasis in gastric carcinoma.