Several years ago, when the discovery of catalytic RNA was recognized in a public manner, many people asked if new ?elds of therapy would soon be available. Although some tentative positive answers were given, nobody would say with certainty that RNA of various kinds was a truly promising means of altering gene expression. In fact, over the past decade, both our knowledge of RNAs with different functions and the utility of RNA in the inhibition or enhancement of gene expression have occurred with great drama. We proceeded in terms of possible therapeutic tools from RNase P and group I introns...