Even though school bullying is not a new phenomenon, one of the major difficulties in .considering bullying is that it is not a phenomenon which is easily defined and measured: teachers and other professionals have underestimated the extent of the problem and the long-term trauma and damage caused both to the victims and bullies. Bullying is simply one form of aggression which is social in its nature, and bullying in schools is one of the dark, hidden areas of social interaction. Bullying is a serious problem in most schools not only in Japan, but also in America, Western Europe, and Scandinavian countries. Through observing American schools' condition, it was found that a single teacher or counselor could not handle the problem of bullying, but a whole school intervention was effective for the problem. It was suggested that such an intervention program had better contain the following concepts: remedial, preventive, and developmental. According to the concepts, "Ijime Prevention Curriculum (IPC)" which is one of psychoeducational programs was proposed for Japanese schools in order to treat school bullies.