The purpose of this article is to assess the value of maternal serum triple marker screening of α-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) for the prenatal diagnosis of fetal chromosomal abnormalities in Korean women of advanced maternal age. Maternal sera were collected from 458 pregnant Korean women aged 35 between 15 and 20 weeks gestation before amniocentesis. A patient-specific second trimester risk for fetal Down's syndrome was calculated using the median values for AFP, hCG, uE₃ and maternal age. Twelve fetal chromosomal abnormalities were identified. These included six cases of trisomy 21, one case of 46,XY/47,XY,+21, two cases of trisomy 18, one case of trisomy 13, and two cases of 45, X. A cutoff level of 1:200 detected 85.7% (6/7) of the cases of Down's syndrome and 20% (1/5) of the other aneuploidies, with a 27.3% false positive rate. However, a cutoff level of 1:270 did not result in any gains in detecting Down's syndrome or other aneuploidies at the expense of a false positive rate of 34.3%. Second trimester triple marker testing is an effective screening tool for detecting fetal Down's syndrome in Korean women ≥ 35 years old. However, it is not an effective screening tool for non-Down's chromosomal abnormalities.