The presence of mRNAs for vascular endothelial growth factor (VEGF) and a VEGF-related protein, placenta growth factor (PIGF) was examined in 29 cases of renal cell carcinoma tissues and adjacent normal kidney tissues and in 4 human renal cell carcinoma cell lines. Northern blot analysis showed that 26 of 27 hypervascular renal cell carcinoma tissues (96%) exhibited a markedly elevated level (3-13 fold) of VEGF mRNA compared to the adjacent normal kidney tissues. Even tumors of small size, whenever they were hypervascular, overexpressed VEGF mRNA. We also demonstrated that mRNA for PIGF was expressed in 21 of 23 hypervascular renal cell carcinoma tissues (91%) but was not detected in the adjacent normal kidney tissues. Two hypovascular carcinoma tissues neither overexpressed VEGF mRNA nor had PIGF mRNA. VEGF mRNA was detected in four human renal cell carcinoma cell lines, while PIGF mRNA was not. There was no difference in the level of basic fibroblast growth factor mRNA between tumor tissues and normal kidney tissue, although our previous study demonstrated elevated basic fibroblast growth factor protein in the serum of renal cell carcinoma patients (K. Fujimoto et al., Biochem. Biophys. Res. Commun., 180: 386-392, 1991). Taken together, these results suggest that VEGF, PIGF, and basic fibroblast growth factor are cooperatively working to increase the angiogenesis in renal cell carcinoma in vivo.