A total of 6,160 gravidas with gestational ages from 14 to 25 weeks were collected to quantify maternal serum alpha-fetoprotein (MSAFP) using an enzyme immunoassay kit. A level over 2.5 MoM (multiples of the median) was defined as high and a level below 0.4 MoM as low. Ninety-eight women (1.59%) had an initially high MSAFP and 88 (1.42%) a low MSAFP. In the low MSAFP group, 80% returned for a further checkup. Among them, 46% had an over-estimation of gestational age based on their last menstrual period (LMP), 28% had a normal MSAFP and 9% still had a low MSAFP level on a repeat test. Pathologic conditions in other pregnancies included a hydatidiform mole, miscarriage and pseudocyesis. One nonresponder had an ectopic pregnancy. After delivery, no major fetal abnormalities, including trisomy syndromes, were noted in pregnancies carried to term. In the high MSAFP group, 84% returned for check-up. Among them, 15% had an under-estimation of gestational age based on LMP, 16% had twin pregnancies, 46% had a normal MSAFP and 12% still had a high MSAFP on a repeat test. Pathologic conditions in the other pregnancies included one anencephaly, one hydrocephaly and 6 miscarriages. Wrong dating by LMP and false positivity were the most frequent causes of abnormal levels of MSAFP. Two gravidas had artificial abortions because of undue anxiety. MSAFP screening in Taiwan for open neural tube defects does not seem appropriate and using 0.4 MoM as a fixed low cut-off point is inadequate for trisomy syndrome screening. Maternal anxiety should be seriously considered and proper genetic counseling implemented in a screening procedure.