The efficacy of cytological screening in preventing adenocarcinoma of cervix uteri as compared to squamous cell cancer has been evaluated by means of a case-control study in the province of Florence. The odds ratios of women who had a Pap test within the 3 years before the index date was 0.65 (95% confidence interval (CI) 0.26-1.64) and 0.15 (95% CI 0.07-0.31), for adenocarcinoma and squamous cancer, respectively. The duration of the protective effect was shorter in women below the age of 40 years than in older women.