Recently, interest in transcription factor coding genes has emerged in many human diseases. Transcription factors, responding both to extracellular and to intracellular signals, exercise an important regulatory control over the proliferation and differentiation of cells. During the development of CIN (cervical intraepithelial neoplasia) lesions, normal regulation of the cell cycle seems to be disturbed. Transcription factors have been shown in vitro to be intimately involved in the expression of HPV (human papillomavirus) early genes, which affect the development of cervical precancer lesions. To test the relevance of in vitro findings in clinical samples, the expression of transcription factors Skn-1, Oct-1, and AP-2 was analysed in 31 normal cervical epithelial samples and in 55 CIN lesions. The results were correlated with the HPV status and cell proliferation activity of the squamous epithelium as measured by MIB-1 antibody. MIB-1 staining is an applicable marker of CIN, correlating strongly with the CIN grade (P < 0.001). The presence of HPV DNA did not accelerate the cell proliferation rate or change significantly the immunoreactivity of Skn-1, Oct-1, or AP-2 antibodies. The staining patterns of these transcription factors were significantly influenced only by the CIN grade. Transcription factors generally showed weaker expression in the dysplastic samples, although the nuclear staining of AP-2 increased markedly (P = 0.046) in the superficial layer of the CIN III samples. These findings suggest that changes in the expression of transcription factors may be important in studying the proliferative activity of CIN lesions.