To investigate the expression of human papillomavirus type 16 (HPV-16) E5 protein in squamous neoplastic changes in the uterine cervix, the specific E5 antibody was generated and used to identify the expression of E5 protein in 40 cases of HPV-16-positive tissues and 5 previously identified HPV-negative normal cervical tissues. The results revealed that E5 protein was primarily expressed in the lower third of the epithelium in low-grade squamous intraepithelial lesions (SILs) and throughout the whole epithelium in high-grade SILs. In invasive squamous carcinoma, 60% of HPV-16-infected cancers which contained the episomal viral genome had the E5 gene, and could express E5 protein which was located throughout the whole epithelium. Previously, we documented the expression of type I growth factor receptors [ERBB1/EGFR (epidermal growth factor receptor), ERBB2, ERBB3 and ERBB4] in the full range of cervical neoplasias by immunohistochemistry assay. Hence, in this study, we extensively analyzed the correlation between the expression of E5 protein and the expression of type I growth factor receptors. Among 40 HPV-16- infected cervical neoplasias, we found that the expression of E5 protein was significantly correlated with either the expression of the ERBB1 or the ERBB4 receptor.