The neu oncogene codes for a cell surface protein that has a high degree of homology with the epidermal growth factor receptor. Amplification of this oncogene in breast carcinoma and ovarian carcinoma is correlated with a poorer prognosis. The c-myc oncogene codes for a DNA binding protein and is believed to regulate cellular proliferation. Sixteen primary endometrial adenocarcinomas were analyzed for c-myc and c-neu amplification. Eleven of sixteen tumor samples exhibited amplification of the neu gene. Four of these eleven patients died of disease an average of 16 months after diagnosis. The five patients without tumor amplification of the c-neu gene have been followed an average of 31.2 months without evidence of recurrent disease. Ten of fifteen tumor samples exhibited amplification of the c-myc gene. Five of the ten patients died of disease an average of 13.4 months after diagnosis. The remaining five patients have been followed for an average of 31.2 months and are free of disease. Six of the sixteen tumor specimens exhibited amplification of the both c-neu and c-myc genes, and four of these patients died of recurrent disease. Amplification of the c-neu or c-myc oncogene correlated with advanced-stage disease and poorly differentiated lesions, suggesting that oncogene amplification may predict biologically aggressive adenocarcinomas of the endometrium.