Mammary screening was introduced in the capital of Stockholm Sweden at the year of 1989 in the age group between 50 to 69 years.The investigations are performed at radiologic departments with long practice by skilled technicians.In a follow up of two time periods with one sample of from 1991 (17 years follow up) and another from 1987/88 (10 years follow up) we found in the age groups screened a significant reduction in both tumor size at diagnosis and death rate of breast cancer.The sample from 1991 (n =458) was just two years after the introduction of screening and the sample of 1987/88 (n =354) the screening had been in practice for about 8 years.The latter population revealed a stronger reduction in tumors size in the age-screening group and the best result was in the age-group of 60-69 years.The patients had at that age already been included in screening for ten years.We compared tumor size from the year of 1987 when no screening was done and tumor size was reduced at diagnosis from a mean of 23,5±14,8 mm (1987) in the age-group 60-69 years to 17,7±13,8 mm in 1991 and 15,4±12,4 mm in 1997/98 (p<0.001 in both cases related to the unscreened groups).With a reduction in tumor size followed as expected a reduction in the level of proliferation parameters and genomic instability.Death rate after excluding death for other reasons than breast cancer was 1,5 to 2,5 fold lower in the screening age-group as compared to the two unscreened groups below 50 years of age and above 70 years of age.