Pap smears were used only on a limited scale in Denmark until the late 1960s. Since then smears have been taken both in organized screening programs and outside the programs by general practitioners, private gynecologists, and hospital wards. The present smear-taking activity is equivalent to an average of one smear every second year per woman. As the responsibility for health care rests with the counties in Denmark, differences are found between the counties both concerning organization of screening programs, and concerning the overall level of the smear-taking activity. An analysis using multiplicative Poisson models on county-based incidence and mortality data for women aged 30-59 years in 1963-1982 showed a statistically significant effect of organized screening in reducing both the incidence (RR = 0.67; 95% CI, 0.61-0.73), and the mortality (RR = 0.68; 95% CI, 0.59-0.78) of cervical cancer from 5 years after introduction of an organized screening program. The level of overall smear-taking activity was found to be of limited importance when organized screening was taken into account.