Purpose: To argue for and propose bipartite concepts of functioning and disability, to tally with the structure of the ICF classification list, concepts of social models and clinical needs.
Method: The ICF concepts are discussed in relation to the history of ideas regarding disability concepts and the needs for such concepts in interdisciplinary rehabilitation.
Results: Bipartite concepts are presented; they refer to actual functioning, simply body functions/structures and participation, including functioning in standardized environments. Participation refers to actually performed "activities", with "activities" simply denoting things that people may do. Bipartite concepts are congruent with the ICF classification and the structure of social models of disability, suitable for clinical and interdisciplinary use and easy to understand. The issue of standardized environments represents a methodological issue rather than the conceptual issue of defining functioning and disability. An individual perspective on activity and activity limitations, i.e. the middle part of the tripartite ICF concept, is somewhat similar to concepts of traditional language that were regarded as too generalizing already in 1912, when the interactional concept of "disability in a social sense" was introduced in rehabilitation practices.
Conclusion: Bipartite concepts of functioning and disability are recommended for interdisciplinary use of the ICF.
Implications for rehabilitation: The ICF classification is useful, but the ICF concept of activities in an individual perspective is confusing. We suggest a use of the term "activities" simply to denote things that people may do and "participation" to denote actually performed activities. Estimations of ability should be explicit about how they are related to environmental factors.
Keywords: Activity limitation; ICF; interaction; interdisciplinary; participation; social model.