Background. Considerable controversy and limited information surrounds the use of performance-based functional assessments for determining an injured worker's ability to function at work. Purpose. Amidst a variety of protocols, philosophies and tools, the key aspects of different assessment approaches are described and compared across a range of assessment provider organizations. Method. Qualitative and quantitative strategies were used to generate an in-depth understanding of the different assessment practices among 23 Southern Ontario assessment providers. Results. Assessment approaches share common elements and variations that can be described along the continua of five dimensions: nature of assessor-evaluee interactions, fixed or flexible protocol delivery, efforts to contextualize, perceptions and use of evidence, and provider organizational environment. These approach dimensions are offered as a focus for appraising practices. Practice Implications. Assessors need to reflect upon to what extent they are using a whole person, client-centred approach directed by clinical reasoning amidst a market driven industry.