The overall objective of this doctoral thesis is to address some of the conditions necessary to routinely perform alongside economic evaluations of rehabilitation programs. The specific aims are to 1) present a standardized instrument to collect data about health care resource use, 2) identify major cost categories of direct medical costs to be used in comparative economic evaluations of subjects with musculoskeletal diseases and 3) identify determinants of direct medical costs among subjects with musculoskeletal diseases. This thesis is therefore subdivided into three parts. In the first part the development of a standardized instrument to collect health care resource use in the context of rehabilitation is described and lessons learned are discussed. In the next part major direct medical costs categories among patients with musculoskeletal conditions undergoing outpatient rehabilitation are identified. Lastly, the determinants of the direct medical costs as well as direct medical costs beyond the median incurred by chronic musculoskeletal patients are examined. Each of these parts contain a specific discussion section referring to its specific results.