The Reflective Interaction Observation Scale (RIOS) describes and operationalizes the nature of the interactions between a supervisor and supervisee(s) during reflective supervision. Developed in collaboration among researchers and clinicians from the University of Minnesota, the Minnesota Association for Infant and Early Childhood Mental Health, and the Alliance for the Advancement of Infant Mental Health, the RIOS is organized around five core Essential Elements that constitute the content of the discussion conducted between the supervisor and supervisee during a reflective session: Understanding the Family Story, Holding the Baby in Mind, Professional Use of Self, Parallel Process, and Reflective Alliance. Interactions between supervisor and supervisee(s) are identified as Collaborative Tasks: Describing, Responding, Exploring, Linking, and Integrating. The RIOS coding process captures the nature of interactions during a supervision session and can demonstrate the progression of the relationship over time.