The term “extremophiles” is used for organisms that thrive under extreme conditions, and are designated the enzymes that are active and tolerant under extreme reaction conditions “extremozymes”. We have long been engaged in the screening, gene cloning, and industrial applications of alkaline enzymes from alkaliphilic bacilli. Alkaliphilic bacilli have made a great impact on the detergent industry, because they often produce alkaline enzymes that improve the detergency of detergents. We isolated a number of alkaline enzymes from alkaliphiles, such as cellulase, α-amylase, protease, mannanase, and pectate lyase. We incorporated an alkaline cellulase into super-compact detergents for the first time in the world. Some of the alkaline enzymes were crystallized, and their tertiary structures were determined. The alkaline adaptation mechanism of these enzymes was analyzed by determination of the amino acid substitutions that and deletions occur during the alkaline adaptation process. The alkaline adaptation appeared to be a remodeling of ion pairs so that the charge balance is kept in the high alkaline pH range.