This Compliance Data System (CDS) User's Guide is designed to be the primary source of user documentation regarding CDS. It replaces all documentation dated prior to March 1978, which should be discarded. The guide is organized to be used effectively by several groups of potential readers: Managers and others wishing a basic description of CDS should read Sections 2 and 3, Management Overview and System Applications. Current Users who generally understand CDS will wish to skip to specific sections of interest, particularly Sections 7 and 9, Edit Processing and Retrieval Processing, which reflect recent changes. New Users may wish to read the text in its entirety, at least through Section 9 to obtain a working knowledge of CDS. Those Preparing Input Data should read Section 6, Data Input Preparation. CDS was developed to assist EPA's Regional Offices in implementing their enforcement programs. The primary objective of EPA's stationary enforcement program is to bring about compliance with Federal and State emission requirements as stated by the State Implementation Plans (SIP), the New Source Performance Standards (NSPS), and the National Emissions Standards for Hazardous Air Pollutants (NESHAPS). CDS has been in operation for nearly seven years. Experience with the system has led to modifications and refinements of CDS which are described in detail in this documentation.