What is the bigger challenge-for a student or the instructor to understand what is important in medical microbiology? Many years ago when I took my first graduate course in medical microbiology， I read thou-sands of pages of text， listened to 5 hours oflectures a week， and performed lab exercises 6 hours a week for 1 year. I was given a wonderful foundation in micro-biology， but I frequently asked the question-that was voiced by all the students-do I really need to know all this stuff? The answer to that question is certainly no， but the challenge is what information is needed.Years later when I set out to write my first textbook on microbiology， my goal was to only give the students what they need to know， described in a way that is informative， factual， and concise. I think I was success-ful in that effort， but I also realize that the discipline of microbiology continues to change as do approaches to presenting information to the students. i am still firmly convinced that my efforts in my first textbook， Medical Microbiology， and subsequent editions are important，forming the foundation of microbiology knowledge for a student. This cannot be replaced by a quick search of the internet or a published review because much of the subject matter presented in Medical Microbiology-epidemiology， virulence， clinical diseases， diagnostics，treatment-is a distillation of the review of numerous research articles and clinical and technical experience.Having stated that， students frequently turn to review books consisting of abbreviated summaries， illustra-tions （should I say cartoons）， and various mnemonic aids for mastering this subject. As I have watched this evolution oflearning microbiology， I am struck by the sacrifice that has been made. I believe microbiology is a beautiful subject， with the balance between health and disease defined by the biology ofindvidual organisms and microbial communities. Without an understand-ing of the biology，lists of facts are soon forgotten. But I am a realist and know the burden students face， master-ing not only microbiology but also a number of other subjects. So the personal question I posed was-is there a better way to present to the student a summary of information that is easy to understand and remem-
　　 ber? This book is my approach to solving this question.
　　 First， almost by definition， it is not comprehensive. Just as I have carefully selected organisms and diseases to present in this book， I have also intentionally not men-tioned others-not because they are unimportant but because they are less common. I have also not presented a detailed discussion of microbial biology and virulence or the immune response of the patient to an infection，but simply presented the association between an organ-ism and disease. Again， I felt those discussions should be reserved for Medical Microbiology. Finally， the orga-nization ofthis book is focused on organisms-bacteria，viruses， fungi， and parasites-rather than diseases. I do this because I thinkit is easier for a student to remember a limited number of diseases assoaated with an organ-ism rather than a long list of organisms （or a signifi-cantly incomplete list） implicated in a specific disease such as pneumonia. Still， patients present with disease and the observer must develop a list of organisms that could be responsible； so to aid the student， i provide this differential diagnosis in the introductory chapter of each organism section （Chapters 2， 12， 18， and 22）.I also provide in these introductory chapters an over-view of the classification of the organisms （a structural framework for remembering the organisms） and a list-ing of antimicrobials that are used to treat infections.The individual chapters in Sections 1-4 are organized in a common theme： brief discussion of the individual organisms， a summary of facts （properties， epidemiol-ogy， clinical disease， diagnosis， treatment） provided in a conase table， illustrations provided as a visuallearning aid， and clinical cases to reenforce the clinical signifi-cance of the organisms. Finally， examination questions are provided to help the student assess their ability to assinulate this material. Again， I will emphasize that this text should not be considered a comprehensive review of microbiology. On the other hand， I believe if the student masters this material， he or she will have a firm foundation in the principles and applications of microbiology. I certainly welcome all comments on how successful my efforts are.
　　 I would like to acknowledge the support and guid-ance from the Elsevier professionals who help bring this concept to reality， particularly Jim Merritt， Katie DeFrancesco， Nicole DiCicco， and Tara Delaney.
　　 Additionally， I want to thank the many students who have challenged me to think about broad world of microbes and distill this into the essential material they must master， and my professional business col-leagues who stimulated me to explain complex micro-biology information in a factual but coherent story for a novice in this field.