UK breast screening policy currently restricts routine 3-yearly invitation to screening to 50-64 year olds. However, it is likely that routine invitation will be extended to 65-67 year olds in 2001. This paper first predicts the additional demand for breast screening as a result of this new policy by modelling the response to the 1998 invitation of women eligible for screening in 2001. The independent variables include (i) the woman's characteristics: her screening history; the deprivation score of the area she lives in: and (ii) the characteristics of the screening: whether the screening took place in a mobile van or at a static site; and time of the year. The modelling of attendance is quite successful in that most hypothesised variables have the expected sign. It is estimated that an additional 10 829 women will be screened per annum. The additional invitation, screening and assessment costs are expected to be approximately E350 000 in 2001. (C) 2001 Elsevier Science Ltd. All rights reserved.