Differences in the tumor biology of ovarian carcinomas probably influence operability and response to chemotherapy which are the most relevant prognostic factors. The phenotype of different malignant epithelial tumors including ovarian carcinomas is obviously associated with an activation of the EGF/TGFa signal pathway. When we analysed the expression of EGF-R and TGFa with biochemical, molecular-chemical and immunohistochemical methods in 29 different ovarian carcinomas, we found a correlation between the mRNA and protein levels of EGF-R as well as TGFa for tumors with low or high expressing rates. However, the concentration of measurable free EGF-Rs seems to depend on the amount of TGFa expression by the tumors. The EGF-R binding ligand TGFa is produced by the tumor cells; stromal cells are TGFa negative as shown by immunohistochemistry. By the use of an immunostaining index the TGFa protein concentration was measured semiquantitatively, classifying tumors according to their TGFa production rate. The comparison of TGFa mRNA amounts and staining index supports the hypothesis that TGFa is modified posttranslationally. EGF-R or TGFa expressing ovarian carcinomas had a high response rate to chemotherapy, whereas the EGF-R or TGFa negative tumors mostly exhibit a no change or progressive disease behaviour. These findings are the basis for our assumption that ovarian carcinomas with the basis for our assumption that ovarian carcinomas with an activated EGF-TGFa system are tumor biologically different compared to the EGF-R/TGFa negative tumors.