Objective: The pain physician is often asked to establish the medical impairment of the chronic pain patient (CPP) and from that determination ascertain the work capacity of the CPP. Functional capacity (FC) testing has recently been introduced as a more objective and accurate way of facilitating the determination of work capacity. However, there are conceptual problems with the measurement of FC. These will be reviewed and the relationship of FC to residual functional capacity (RFC) will be determined. Finally, a method for measuring RFC in a job-specific manner will be suggested.Data Sources: The literature in reference to the measurement of medical impairment, FC, and RFC was reviewed.Study Selection: Studies appropriate to the objective of this review were selected for inclusion.Conclusions: The FC and RFC are poorly defined. Lack of definition has interfered with design of appropriate test batteries specific to work capacity. To circumvent this problem a job-specific RFC measurement method is suggested. This method is based on theDictionary of Occupational Titles.