Clinico-pathologic, epidemiologic and molecular analytic studies have shown that: i) the squamous cancer of the uterine cervix derives from intraepithelial lesions with different degrees of atypia; ii) human papillomavirus (HPV) can play a fundamental role in the progression of these lesions. We have examined 219 uterine cervix biopsies by means of the in situ hybridization technique (ISH) using biotinylated probes for 6/11, 16/18 and 31/35/51 HPV strains. The histologic lesions were as follows: 104 (49.7%) focal koilocytotic lesions 26 (11.8%) low grade intraepithelial lesions (SIL) 45 (20.5%) high grade intraepithelial lesions (SIL) 18 (8.2%) condylomata acuminata 21 (9.8%) invasive cancers. The percentage of the positivity found in the whole material examined is 14.1%. In particular, none of the 109 cases of focal koilocytotic lesions was positive, whereas the 28.1% of the remaining 110 biopsies turned out to contain HPV. We hypothesize that our small percentage of positivity in preinvasive and invasive lesions of the uterine cervix can be due to the fact that the HPV is not the only cancerogenic factor involved, although the possibility of a low sensitivity of the technique cannot completely be excluded.