This book is ready to digest compilation for the students of dentistry in general and Periodontology in particular. Care has been taken to include all the important aspects of Aggregatibacter Actinomycetemcomitans while simultaneously keeping it as precise as possible. A. a is one of the most important organism studied in Periodontology. Much has been discovered about A. a, but lot is yet to be revealed. This work is expected to help students and researchers to gain a deep insight of the microorganism and research further.