Since the publication of randomised trials showing firm evidence of prevention of neural tube defects with periconceptional folic acid, there have been population health promotion programmes to encourage women to take folic acid supplements, and the introduction of voluntary fortification of some foods with folic acid in Australia. In order to evaluate these two strategies, we collected data by self-administered questionnaire from a random sample of recently pregnant women in Western Australia between September 1997 and March 2000. Response to health promotion was measured in three ways: (1) knowledge of the association between periconceptional folate and prevention of spina bifida (the 'correct message'); (2) use of periconceptional vitamin supplements of folic acid daily in the periconceptional period; and (3) daily folate intake from fortified foods in the 6 months before pregnancy. We examined the relationship of maternal demographic and behavioural characteristics with these three measures. Overall, 62.3% of women were aware of the correct message before pregnancy, 28.5% reported taking 200 microg or more of folic acid from supplements daily in the periconceptional period and 56.6% of women obtained 100 microg or more of folic acid from fortified foods. Women who first became aware of the correct message during pregnancy or who were unaware of the correct message before or during pregnancy were more likely than women aware before pregnancy to be younger, having their first pregnancy, be single or in a de facto relationship, have no tertiary education, and be a public patient. Similar associations were seen for women taking either no folic acid or < 200 microg of folic acid in supplements daily in the periconceptional period. There were no significant associations between these demographic variables and amount of folate obtained from fortified foods. Women who were unaware of the correct message and did not take folic acid supplements were more likely to have smoked, not to have engaged in exercise, and not to have planned their pregnancy, whereas there was no association with these behavioural characteristics and intake of folate from fortified foods. These results indicate that health promotion strategies have not reached all segments of the target population equally, but there is no such disparity with folate-fortified foods, and they suggest that mandatory fortification of a staple food is likely to reach all women regardless of demographic and behavioural characteristics, and hence provide improved opportunity for prevention of neural tube defects in Australia.