OBJECTIVE: This article discusses the use of a third qualifier, subjective experience of involvement, as a supplement to the qualifiers of capacity and performance, to anchor activity and participation as separate endpoints on a continuum of actions. DESIGN: Empirical data from correlational studies were used for secondary analyses. The analyses were focused on the conceptual roots of the participation construct as indicated by the focus of policy documents, the support for a third qualifier as indicated by correlational data, differences between self-ratings and ratings by others in measuring subjective experience of involvement, and the empirical support for a split between activity and participation in different domains of the activity and participation component. RESULTS: Participation seems to have two conceptual roots, one sociologic and one psychologic. The correlational pattern between the qualifiers of capacity, performance, and subjective experience of involvement indicates a possible split between activity and participation. Self-ratings of participation provide information not obtained through ratings by others, and later domains in the activities and participation component fit better with measures of experienced involvement than earlier domains did. CONCLUSIONS: The results from secondary analyses provide preliminary support for the use of a third qualifier measuring subjective experience of involvement to facilitate the split between activity and participation in the International Classification of Functioning, Disability and Health, Children and Youth version, activity and participation domain.