The economic consequences of using an index of maternal age and maternal serum alpha-fetoprotein (MSAFP) screening to indicate risk of Down syndrome (DS) are examined. If DS screening indicated solely by a given maternal age is economically justifiable, then amniocentesis indicated by a DS risk equivalent to that maternal age cutoff, but based on an index of maternal age (for ages below the cutoff) and low MSAFP results, is also economically justifiable. It is concluded that the extant use of MSAFP screening for DS is a move toward the cost-effective use of scarce resources that can be made available with coordinated planning. However, increased professional and public awareness may result in significant increases in aggregate demand for these services. While MSAFP screening for DS is economically justifiable, there exists some potential for bottlenecks at the aggregate level, and these should be considered in conjunction with recommendations that the technology be adopted on a widespread basis.