This book is about the study of microbes and the funda- mental aspects of microorganisms and their relationship to agriculture. Designed for undergraduate and postgraduate students of agriculture and biology, this basic and well illustrated text provides a comprehensive presentation of microorganisms. The book begins with some basic information on micro- organisms including methods of study and classification. It then goes on to describe their morphology, physiology, biochemistry and genetics. A discussion on soil micro- organisms along with pathogenic forms and their effect on plants is also given. The text concludes with a fairly detailed account of microbial biotechnology which covers most of the recent advances in the area. This is the second edition of the author’s highly successful earlier edition for which Dr. Selman A. Waksman, dis- coverer of Streptomycin, write the Foreword. The author worked with this Nobel Laureate at Rutgers State University.