This article presents the idea that databases are very useful tools for teaching languages over the Internet. Databases in Computer Assisted Language Learning (CALL) are commonly used in three ways: for reference sources such as dictionaries, in the management of large websites, and for data processing such as language tests and learners' profiling. Such types of use are illustrated by a number of databases that are described in detail in this article. A basic description of the construction of an interactive database is also provided.