Children with high-functioning autism (HFA) and Asperger’s syndrome (AS) experience considerable impairment in their day-to-day social interactions. While interventions such as social skills training programs have been developed to address these concerns, there is a lack of ecologically-valid measures to assess meaningful outcomes in children’s social interactions. The current study utilized a qualitative approach to develop the Social Interactions Behavior Inventory (SIBI), a parent- and child-report measure examining children’s social functioning in the school, community, and home settings. An initial pool of items was generated based on the social functioning literature of children with HFA/AS and expert consultation. Focus groups and individual interviews were conducted to obtain parents’ and children’s feedback regarding the SIBI, and four iterations were completed until a final parent and child version was deemed adequate and satisfactory. Issues regarding parent-child agreement, the use of child self-reports, and parents’ knowledge of children’s school social behaviors are discussed. Future studies examining the psychometric properties of the SIBI in larger, more representative samples are warranted.