Maternal serum alpha-fetoprotein screening will soon be a routine component of prenatal care. The benefits of MSAFP screening have far exceeded early expectations. This technology not only provides an efficient and cost effective method of screening for fetal neural tube defects that is applicable to all pregnancies but also provides the physician with important information relevant to other complications of pregnancy. Maternal serum alpha-fetoprotein screening may also prove to be a significant tool for the early detection of Down's syndrome and other chromosomal abnormalities. Our knowledge of variables affecting MSAFP levels measured during pregnancy is rapidly evolving and further refinements in the application of MSAFP screening will almost certainly occur. Such refinements can only serve to extend the benefits of this new and very valuable technology in improving the health and well-being of mothers and infants.