The objectives of this study were to confirm the hypothesis that invasive carcinoma of the uterine cervix and the precursors of that condition are most often caused by human papilloma virus (HPV) infections, and to determine whether or not other risk factors are involved in the neoplastic process. For this purpose, four concurrent case-control studies were carried out. Two included cases of invasive cervical cancer and population- based controls. The other two included cases of in situ carcinoma and controls. Research was carried out in nine provinces of Spain and in Cali, Colombia. The identification of cases took place between june 1985 and june 1988