Two groups of pregnant women were questioned regarding their opinions on serum screening for Down's syndrome in the first trimester of pregnancy. One group comprised 83 women attending our antenatal clinic who were questioned at the time of the existing second-trimester screening test. Seventy-six per cent of those who participated in the second-trimester screening programme would have preferred the test to have been in the first trimester, mainly because of the easier termination of pregnancy and/or the earlier reassurance provided. The remaining 24 per cent could see no advantage in the earlier time frame. Of the 49 women who had declined second-trimester screening, only two would have participated in screening had it been in the first trimester. The other group comprised those women attending our antenatal diagnosis clinic who were considering chorionic villus sampling (CVS). Forty-four per cent of these women would have allowed serum screening in the first trimester to influence their decision as to whether to undergo definitive prenatal diagnostic testing. In general, those women who made use of second-trimester serum screening would also do so in the first trimester. Those who declined the existing screening programme would also decline first-trimester screening. Many women currently deciding to undergo CVS would allow a first-trimester screening test to influence their decision. 1997 by John Wiley & Sons, Ltd.