The Motivational Interviewing with Significant Others (MISO) coding system measures the language and behaviors of significant others (SO) participating in motivational interviewing sessions. This coding system can be used in conjunction with the MISC 2.1 coding system in a single pass. Thus, client, therapist, and SO language can be coded at the same time. The MISO consists of three global ratings of SO behavior: collaboration, support, and contemptuousness, as well as 11 behavior counts. The MISO coding manual can be downloaded here.