Overexpression of the erbB-1 (EGFR, epidermal growth factor receptor) and erbB-2 (HER2/neu) proteins contributes to the aggressive behavior of malignant tumors originating from the endometrium. We currently examined whether the trend of these proteins to overexpression is a direct effect of their gene transcriptional activities. Expression of the erbB-1/erbB-2 genes was measured applying the quantitative RT-PCR technique in 25 uterine carcinomas, 12 normal endometria, a carcinosarcoma and a case of botryoid sarcoma of the uterine cervix. We showed that erbB-1 mRNA was overexpressed in 48% (12/25) and erbB-2 mRNA was overexpressed in 8% (2/25) of the analysed tumors. The level of expression appeared to be significantly higher in the malignant tumors as compared to the benign ones for erbB-1 and for erbB-2 (p=0.0001 and p=0.008, respectively). A significant correlation between erbB-1 overexpression and tumor differentiation was found (Spearman rank correlation test, p<0.001). Concomitant erbB-1 and erbB-2 overexpression was detected only in 1 out of 25 (4%) uterine neoplasms. erbB-1 was overexpressed in a sarcoma botryoides of the uterine cervix. Our data suggest that erbB-1/erbB-2 overexpression is a direct effect of higher than normal transcriptional activity of the encoding genes in a subset of human endometrial carcinomas.