Data collected by questionnaire from 89,835 women on entry into 15 Canadian National Breast Screening Study (NBSS) centres reveal pre-recruitment sources of awareness: radio and television were reported by 30%; workplace 6%; friends 35%; physician 6%; and other by 23% of respondents. Personalized letters of invitation employed in 5 centres were an important source of awareness. In the age group recruited, 40-59 years, age had no influence on the source reported. However women with post-secondary school education were less likely to report radio and television as a source and more likely to report newspapers compared to women with less education. Women with only public school education were less likely to report the workplace as a source of awareness than women with post-secondary education. Recruitment strategies for screening programs may be more successful if publicity on radio and television is geared to women of lower educational status and if publicity in newspapers is geared to women of higher educational status, supplementing both with personalized letters of invitation.