The purpose of this study was to validate the Swedish translation of the Assessment of Communication and Interaction Skills (ACIS-S) and its applicability in Sweden. The ACIS is an observational rating scale designed to capture, in detail, a person's social interactional ability, while he/she is participating in meaningful occupations. Eighteen occupational therapists trained in administering the ACIS-S, completed 157 ACIS-S assessments of 67 subjects with psychosocial and learning disabilities. Many-faceted Rasch analysis was used to analyse the data. The results supported internal, construct and person response validity of the ACIS-S, and rater validity and reliability. The scale effectively categorized subjects according to the levels of communication and interaction ability.