The capacities of RNA for both catalysis and molecular recognition have been appreciated for some time. Recently, a number of studies have shown that these distinct functional classes may be combined to generate multipartite ribozymes in which the catalytic and ligand-binding elements act coordinately. In this chapter, we describe a procedure known as allosteric selection, in which an RNA catalyst in conjunction with a random sequence domain is subjected to iterative in vitro selection in order selectively to recover ligand-dependent ribozymes.