EPA has supported the National Pretreatment Program by developing numerous guidance manuals. In fact, it has released more than 40 manuals providing guidance to EPA, states, POTWs, and industry on various National Pretreatment Program requirements and policy determinations. Through such guidance, the National Pretreatment Program has maintained national consistency in interpreting the regulations. Nonetheless, turnover in National Pretreatment Program staff has diluted historical knowledge, and new staff and other interested parties might be unfamiliar with existing guidance materials. With this in mind, the intent of this guidance manual, Introduction to the National Pretreatment Program, is to: Provide a reference for anyone interested in understanding the basics of National Pretreatment Program requirements; and Provide a road map to additional and more detailed guidance materials for those trying to implement specific elements of the National Pretreatment Program. This guidance manual is intended to explain the basic concepts that shape the National Pretreatment Program, discuss the current status of the program and program guidance, and serve as a tool for pretreatment program implementation. The manual is organized to provide an overview of program requirements and to refer the reader to more detailed EPA guidance on specific program elements. To help the reader, the first page of each chapter contains a list of EPA references applicable to the topics discussed in that chapter.