Changes in rehabilitation and clinical practice, the recognition of the role of clients in achieving rehabilitation goals, and client participation in decision-making and administration of service delivery have contributed to the development of new methodologies for research and evaluation. In this paper, the traditional relationship between researchers and subjects in traditional rehabilitation evaluation and research is contrasted with relationships between researchers and clients-consumers in newer methodologies. The limitations and challenges to these models are discussed. Collaborative research, characterized by shared power and non-hierarchical authority between client-consumers and researchers, is described as an alternative model for experimental and evaluative research. Collaborative relationships provide a structure for building upon the knowledge and expertise of each research partner. The authors draw upon their own experience of collaborative research partnerships and models of research partnerships are described. Research developed and conducted in a collaborative partnership can include quantitative and qualitative approaches, maintain traditional scientific perspectives of objectivity, reliability and replicability, and improve participation rates, continuity of involvement for longitudinal studies and utilization of researched methods into practice.