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We describe the long-term follow-up of a closed cohort of 44349 women first invited to screening between January 1, 1989, and September 30, 1990. For all members of the cohort, screening histories up to September 30, 1999 were obtained. Individual records were matched with the North West Regional Cancer Registry and the NHS Central Register to determine all breast cancers occurring before December 31, 1998, deaths that have occurred before December 31, 1999 and losses to follow-up during the study period. This has allowed us to identify, for the first time, inter alia compliance with invitations to repeated screening, occurrence of cancers and deaths in non-attenders and the distribution of cancers and deaths in women attending screening.

Nine-hundred and twenty-one cancers were identified after the first invitation to screening and 155 women died of breast cancer. Preliminary findings suggest that only 53% of women invited to four routine screens attend every screen. The incidence of breast cancer in non-attenders is low, but their survival is poor. In 443 women, cancers were detected at screening; 43 (10%) died of breast cancer. In 222 women, cancers were detected in the interval between screens; 49 (22%) died of breast cancer.