Naturally occurring RNA molecules exhibit many unexpected and fascinating properties in living cells like protein synthesis and transport, regulation of metabolic functions, and catalytic cleavage reactions. To understand this functional diversity, a detailed knowledge of RNA structure and metal ion-binding properties is crucial. In our research group, we address these problems by combining various biochemical, analytical and spectroscopic techniques. A large part of our work is devoted to the structure determination of catalytic RNA molecules, i.e. ribozymes, by NMR. Based on the three-dimensional structure, further experiments are carried out to understand in detail the effects of different metal ions on the local and global structure, as well as catalysis itself.