The Environmental Monitoring Methods Index System (EMMI) is an automated inventory of information on environmentally significant analytes monitored by the U.S. Environmental Protection Agency (USEPA) and methods for their analysis. The EMMI System was originally developed in 1985 by Viar and Company and Joel Karnofsky for the USEPA Office of Water Regulations and Standards (OWRS) Industrial Technology Division (ITD) to aid in the selection of appropriate analytical methods for environmental monitoring studies. In November 1990, the Agency selected the EMMI System, then called the List of Lists, for enhancement and distribution throughout EPA to serve as the single authoritative source for cataloguing the Agency's analytical methods. The EMMI database includes information on more than 2600 analytes from 50 regulatory and non-regulatory lists and more than 900 analytical methods. The database provides a comprehensive cross-reference between analytes and analytical methods and contains information on related laws and organizations and additional databases for further information. EMMI is a PC-based system written in System J and will run on IBM and IBM-compatible personal computers. EMMI software is available in a run-time module that allows users to execute the application but does not allow any modification of program or database files. System change control is maintained by the USEPA Office of Water.