This book will help us expand further into chemical engineering and help the reader become a licensed professional engineer (PE), which can offer a tremendous boost to one's career, as there are certain career opportunities available only to licensed engineers. Licensure demonstrates high standards of professionalism, knowledge, and ability. There are four main steps to getting licensed as a professional engineer. Each state and territory varies slightly, but in general one must graduate from an ABET-accredited engineering program, pass the fundamentals of engineering exam, gain work experience, and then pass the PE exam. Because of the work experience requirement, PE examinees have generally been out of school for some time. This book summarizes the theoretical background of topics covered in the exam, which will help potential examinees refresh their memories on subjects they may not have been exposed to since their undergraduate classes. Another advantage of using this book to prepare for the PE exam is that two or three 'logical distractors' (answers that result from common mistakes) are included among the answer choices for each problem. The solutions to the problems also explain why the logical distractors are incorrect. Research has shown that this is an efficient teaching tool. Thus, the inclusion of these logical distractors and their explanations will give individuals a better foundation in the subject matter in a shorter period of time. Although this book is intended primarily to help engineers prepare for the PE environmental engineering examination, it will also be useful in undergraduate engineering courses that cover environmental engineering topics. The introduction contains hints for successful completion of the exam and information on how to use this book. Chapters 2 through 5 consist of a summary of relevant theory and multiple-choice sample examination problems for the four main topic areas of the exam (water, solid and hazardous waste, air, and environmental health, safety, and welfare). The more than 100 sample problems presented in Chapters 2 through 5 are in the same multiple-choice format as the actual exam, and detailed solutions are provided. An additional 100 original multiple-choice problems are provided in the Sample Exam in Chapter 6, again with detailed, step-by-step solutions. The topic distribution of the problems in Chapters 2 through 5 and in Chapter 6 matches the NCEES descriptions of material covered in the examination, and topics covered in the chapters closely follow the syllabus published by NCEES for the Principals and Practice of Environmental Engineering exam. In addition to being a preparation text for potential examinees of the PE Environmental Engineering exam, this book will be an excellent reference text for students in undergraduate environmental, civil, and chemical engineering programs.