The aim of this study was to evaluate the effects of screening for cancer in the Nordic countries. There is sufficient scientific evidence to conclude that screening for cervical cancer, breast cancer and colorectal cancer will result in a reduction in mortality. The effects on mortality were predicted for the future up to the year 2017 assuming that the Nordic countries are covered by screening as a nation-wide population-based public health policy and comparing the predicted mortality trends with those assuming no screening programmes. For cervical cancer the programme as practised in Finland was used as a point of reference. For breast cancer and for colorectal cancer the results of randomized preventive trials were assumed in the absence of detailed results based on any public health policy, i.e., a reduction of 30% in mortality from breast cancer and 20% in mortality from colorectal cancer. The assumed ages and frequencies of screening ranged from 25 to 59 years at 5-year intervals for cervical cancer, from 50 to 69 at 2-year intervals for breast cancer and annual screening from 50 to 74 years for colorectal cancer. Data on incidence and incidence predicted up to the year 2012, mortality, survival and size of the general population were employed in the estimation. Age-cohort and age-period-cohort log-linear models were applied in predicting future mortality rates with and without screening. The choice of the models depended on the age distribution of deaths from each particular site of cancer, on changes in public health policy, such as establishment of mass-screening, and on the goodness of fit of the model. The screening policy assumed would result in 1600 annual deaths prevented out of the potential 13,600 deaths in the Nordic countries in 1995, corresponding to 11% of the deaths from the three primary sites. Only after the year 2010 will the ultimate effect of such a screening policy have as full an effect and in 2013-2017 the annual number of cancer deaths prevented will be 3900 out of 15,000 potential deaths, i.e., a 26% reduction. This is equal to 5.7% of all cancer deaths in the Nordic countries in 2013-2017 (2.0% for males and 9.7% for females). The predicted numbers of annual deaths prevented in 2013-2017 are 1500 for cervical cancer, 1000 for breast cancer and 1500 for colorectal cancer. Most (91%) of the cervical cancers can be prevented, whereas the proportion of breast cancer deaths (18%) and colorectal cancer deaths (18%) prevented will be much smaller. Costs of the screening programmes were estimated taking into consideration the direct costs of screening and savings from advanced disease treatment and terminal care. The total cost of screening for cervical, breast and colorectal cancer in the Nordic countries in the year 2010 is estimated to be $111 m. Cervical cancer screening is estimated to save $17 m yearly in the period 2008-2012. Screening for cervical cancer is approaching a phase when both the effect and costs are relatively stable and it was estimated to be cost-saving. The effect of screening for breast and colorectal cancers is expected to become apparent gradually during the predicted period due to the increasing number (and percentage) of patients diagnosed by screening. When the screening programmes are assumed to achieve the optimal effect, the reduction in mortality will increase and treatment costs fall, resulting in a substantial decrease in the cost-effectiveness ratio. In the last considered period (2008-2012) the costs per life year gained (breast cancer $15,400, colorectal cancer $5700) are approximately one half of those at the onset of screening. The differences in the costs per LYG were relatively small between the Nordic countries and mainly dependent on the differences in baseline risk of cancer. The total cost of the three screening programmes was estimated at $4400 per life years gained in the year 2010.(ABSTRACT TRUNCATED)