Transabdominal chorionic villus sampling (TA-CVS) was performed in 707 viable singleton pregnancies to exclude chromosomal abnormalities. Maternal age ranged between 36 and 49 years (mean 37.9 years); gestational age varied between 10.2 and 18.3 weeks (mean 13.3 weeks). In 639 women (90.4 per cent), a sufficient amount of chorionic tissue (greater than or equal to 10 mg) was obtained after one needle insertion; in 66 women (9.3 per cent) two insertions were needed. An abnormal chromosome pattern was established in 19 cases (2.9 per cent). Vaginal bleeding or spotting within 28 days after TA-CVS occurred in 11 cases (1.5 per cent). The completed follow-up of 678 chromosomally normal pregnancies showed an overall fetal loss rate of 2.6 per cent before 28 weeks. The overall perinatal mortality was 0.9 per cent. When relating fetal loss to gestational age at TA-CVS, this was 6.6 per cent in women sampled before 12 weeks against only 1.8 per cent after 12 weeks. At the same time, the percentage of fetal loss occurring within 2 weeks following the procedure was 75 and 30 per cent, respectively. It is suggested that these data reflect the decline in spontaneous abortion rate during this particular period of pregnancy. It is concluded that TA-CVS is an effective procedure which, when performed after the natural decrease of fetal loss, appears to be a safe option for women of advanced maternal age.