Mice produce various sounds with high frequency (USVs) in social contexts. The vocalizations can be acoustically categorized into several syllable types and mice emit different patterns depending on the strain. The vocalizations vary across development and are affected by a housing environment, social experience and motivational state in adults, but the differences of USVs depending on the contexts are still controversial. In this study, we recorded mouse vocalizations during the same- and the inter-sex communications; male-male interaction, male-female interaction and female-female interaction to examine whether mice emit different patterns of the vocalizartions depending on social contexts. Both males and females emitted all types of vcalizations, but males showed longer duration and a greater number of syllables when they encountered a female than those when males and females encountered the same-sex individuals. This longer syllables of male mice were noticeably produced during the mounting behavior, suggesting that this syllable has an important role as a courtship behavior. On the other hand, male mice produced short syllables with upsweep frequency change with a high proportion throughout male-male interaction. Both males and females showed a high proportion of this syllable in early phase when they encounterd a female. These results suggested that the vocalized pattern consisting chiefly of syllables with upsweep frequency change was produced independently of sex and context. In the current study, we found the differences of mouse vocalizations in the same- and inter-sex interaction and the vocalizations consist of several pattern according to a temporal phase of interaction and social context, suggesting that the vocalizations have a different role depending on social context. Our findings provides further studies of mouse ultrasonic vocalizations and understanding of vocal communication. (Work supported by JSPS to YM.)