In this study, we analyzed the use of ‘o/go’ in natural conversations between friends and between first meeting people, and in Japanese intermediate textbooks. Results are summarized as follows. There was no difference between men and women in natural conversations, while men used ‘o/go’ more than women in Japanese intermediate textbooks. For the form of ‘o/go’, simple form was used more than complicated form both in natural conversations and Japanese intermediate textbooks. But, complicated form was is proportional to the age of the talking partners in natural conversations. For the function of ‘o/go’, women had a tendency to use ‘o/go’ as ‘respectful word’ while men had a tendency to use ‘o/go’ as ‘humble word’ in natural conversations between first meeting people. And in the use of ‘o/go’ as ‘beautified word’, there was no difference between men and women. However, in natural conversations between friends, women had a tendency to use ‘o/go’ as ‘beautified word’ while men had a tendency to use ‘o/go’ as ‘respectful word’. In other words, the use of ‘o/go’ is influenced by the age of both speaker and talking partner, the sex of speaker, and the degree od intimacy between speaker and talking partner, etc. But, in Japanese intermediate textbooks, we could not investigate effects of the use of ‘o/go’ because of no showing attribute of the conversation.