main cause for the development of cervical precancer and cancer is a persistent infection with human papillomaviruses (HPVs) of the high-risk group. The E7 protein is one of the major transforming oncoproteins of high-risk HPVs. High-risk E7 protein may be a useful tumor marker for cervical precancer and cancer because it deregulates several cellular pathways, necessary for the oncogenic potential of the virus, by direct protein-protein interaction. Furthermore, high-risk HPV-16, -18, and -45 E7 proteins are continuously expressed in cervical cancer biopsies, but not in biopsies from healthy women, indicating that overexpression of high-risk E7 may be a characteristic feature of cervical cancer. We generated monoclonal rabbit antibodies for the detection of E7 proteins from the most prevalent high-risk HPV types 16, 18, and 45. These antibodies were used to establish a highly sensitive Sandwich-ELISA as a new system for the detection of high-risk E7 oncoprotein in cervical precancer and cancer. The established ELISA format allows to detect recombinant and endogenous high-risk HPV-16, -18, and -45 E7 protein, but does not cross-react with low-risk E7 protein. Furthermore, the established detection system is sensitive enough to detect HPV-16 and -18 E7 in cervical smears from patients, and a correlation between disease status and E7 expression level could be demonstrated in clinical samples.