The talk will begin with a definition of RNA secondary structure, including three different ways to display these structures. Two distinct approaches will be presented for determining secondary structure from sequence data. The comparative method requires a multiple sequence alignment of a collection of homologous RNA sequences. It uses phylogeny to determine common, conserved base pairs that are more likely to be the result of evolution than to exist by chance. On the other hand, recursive algorithms may be used on single sequences to compute minimum free energy structures, partition functions and other biophysical quantities. These algorithms ignore evolution and use empirically derived energy parameters based on physical chemistry. Examples will be given for both methods.