3I (Internet-accessible Interactive Identification) is a set of software tools intended to facilitate developing on-line interactive keys and taxonomic databases. It is based on a customized MS Access database and ASP (Active Server Pages) programming technology. Interactive keys designed using the 3I program have a set of features similar to those of Delta IntKey and Lucid but are specially designed for web publication. Taxonomic databases containing nomenclatural and distributional data, based on taxa, specimens, or both, can be linked to the interactive key or used separately. They allow on-the-fly generation of descriptions and diagnoses of taxa from a data matrix and interactive maps from georeferenced data. Examples of the interactive keys developed using 3I and more detailed information are available from the following web site: http://ctap.inhs.uiuc.edu/dmitriev/.