Because RNA is chemically and structurally dissimilar from protein, the finding of catalytic activity in RNA was initially surprising. Quantitative measurements of reaction rates show that RNA can be as efficient a catalyst as protein. On the other hand, the potential versatility of RNA to catalyze diverse types of reactions has only begun to be explored. Understanding the efficiency and versatility of RNA as a catalyst helps us evaluate origin-of-life scenarios involving self-replicating RNA, and may explain why RNA catalysis remains important in contemporary cells.