Table 1.

Response rate for the Million Women Study^*

Estimated number of women who were sent a questionnaire	227 000
when they were invited for screening
Estimated number who were screened (75% of those invited [1])	170 000
Number of women who returned a questionnaire	121 129	(53% of those invited and 71% of those screened)
Number of women who returned a questionnaire with full	113 104	(50% of those invited, 66% of those screened and
identification details and signed permission for follow-up		93% of those returning a questionnaire)
Number of women who returned a questionnaire without full	8025	(3.5% of those invited, 4.7% of those screened and
identification details and/or signed permission for follow-up		6.6% of those returning a questionnaire)

^*For the first printing of the Million Women Study questionnaire.