There are many ways to represent molecular structures. A drawing is perhaps the most common and useful. It is easy to store drawings of molecules in a computer, but a stored drawing does not constitute a useful computer representation. What is needed is a computer representation that allows structures to be stored and searched in chemically useful and meaningful ways. This is sometimes accomplished by storing a connection table containing atom and bond information. Additionally, 2- or 3-dimensional coordinates are often stored. These data can be stored in files or data structures in some computer language. This chapter introduces ways of representing molecular structures that take advantage of the relational model of data in a RDBMS.