A study is carried out to examine a demonstration project for partial hospitalization rehabilitation of patients of the pension insurance scheme of Rhineland-Palatinate (LVA Rheinland-Pfalz) using a parallel design. In four centers for the rehabilitation of musculoskeletal diseases the patients are assessed at the beginning and at the end of rehabilitation as well as six and twelve months post using the IRES questionnaire, a phycisians' questionnaire for the documentation of medical parameters, an instrument for client satisfaction and additional questionnaires. In addition the treatment and the costs on the side of the pension insurance agency are examined. Partial hospitalization rehabilitation clients are compared to inpatient ones from three rehabilitation hospitals. Preliminary analyses of patient self-report data show a strong similarity of inpatient and partial hospitalization clients as far as admission parameters, rehabilitation treatment, perception of rehabilitation and its effects are concerned. These results indicate that the pension insurance schemes' concept of interdisciplinary rehabilitation can be realized in partial hospitalization rehabilitation centers as well, achieving an outcome very similar to inpatient rehabilitation.