It is the responsibility of professions to provide evidence of the demonstrable value and quality of service delivery. Occupational therapists in mental health care settings find it difficult to produce convincing evidence of the demonstrable value and their contribution to health care. Currently no effective outcome measure for occupational therapists in mental health practices exists for the South African context . The development of an outcomes measuring system is much needed in these crucial times of cost-cutting, rendering quality of care with the minimum resources and the quest for evidence of the effect of intervention. The purpose of this study was to fill the outcome measurement gap by developing a system that is clinically tested and user-friendly for occupational therapists in mental health care settings. Such a system had to represent the outcomes in the occupational therapy programmes, meet the needs of the therapist in terms of purpose of the tool, be easily administered and be standardised. It was also important that the outcome measure was grounded in the theoretical framework that guides intervention programmes, namely Vona du Toit’s Model of Creative Ability. This theoretical framework is widely used in South African mental health care settings and was found suitable to be transformed into a rating scale for the outcome measure. A participatory approach combined with a mixed method exploratory design, specifically the instrument development model, was selected to guide the study. The development of the outcome measure happened in three phases. Domains for the outcome measure emerged after participation from occupational therapy clinicians and mental health care users in Phase 1. The operationalisation of the domains and the development of the rating scale happened during Phase 2. The third phase was the piloting of the outcome measure to identify issues to be optimised for the final implementation of the outcome measure. Eight domains with 52 representative items emerged from Phase 1. The domains were Process skills, Communication and Interaction skills, Lifeskills, Role performance, Balanced lifestyle, Motivation, Self-esteem and Affect. Clinicians were satisfied that these domains represented the service that they deliver and compared well with the mental health care users’ need for occupational therapy. The involvement of mental health care users in confirming relevant domains for the outcome measure ensured a client-centred approach in the research process. The outcome measure, named as the Activity Participation Outcome Measure (APOM), has a unique feature of generating reports and spider graphs for every mental health care user. The APOM was piloted in three mental health care settings. In spite of good intentions from clinicians to apply the measure, it was clear that measuring outcomes is neither a priority, nor a routine task in clinical settings. The preliminary investigation into the psychometric properties yielded positive results. However, the sample sizes for the validity and reliability samples were not optimal and further data collection needs to continue for confirmation. It is recommended that investigations into the psychometric properties of the instrument continue to eventually market it as a valid and reliable outcome measure for occupational therapists in mental health care settings. / Thesis (PhD)--University of Pretoria, 2010. / Occupational Therapy / unrestricted