Recombinant proteins, produced in cells or microorganisms, play an important role in basic research, medical science and the biotechnology industry. Many foreign gene expression systems using mammalian cells, E. coli, insect cells, yeast and other organisms as hosts have been developed. However, only recently has the expression system of Schizosaccharomyces pombe as a host become a subject of focus, as it is expected to be profitable for expressing foreign genes. The reason for this is that S. pombe is evolutionarily more advanced than other types of yeast. This book describes the use of S. pombe in basic research and industrial applications.