The pioneering work of Dr. Koki Horikoshi on the discovery, research and applications of alkaliphilic bacteria are described here in their entirety. The isolation, distribution and taxonomy of alkaliphilic microorganisms as well as their cell structure and physiology are discussed for a basic understanding of these entities. The molecular biology and genome sequencing of some alkaliphilic bacterial strains are also presented. Part II of the volume focuses on enzymes of alkaliphiles and their applications. These include alkaline proteases, starch-degrading enzymes and numerous others. Some of these enzymes are currently in wide commercial use as laundry detergent additives and in wastewater treatment. Alkaliphiles are a relatively recent field of research that will no doubt provide avenues to a wide range of further discoveries and applications for a new generation of workers in bioscience and technology.