In vitro selection is a technique for the isolation of nucleic acid ligands that 
can bind to proteins with high affinity and specificity, and has potential 
applications in the development of new pharmaceuticals. This review summarizes 
the protein targets that have successfully elicited nucleic acid binding species 
(also known as "aptamers") and explores examples of how they might be developed 
for clinical use. In particular, the use of aptamers for the alleviation of 
blood clotting and the treatment of AIDS are considered.