138 patients with end-stage kidney disease and 118 patients with end-stage liver disease were included in an observational cohort study regarding their quality of life. Instruments used were the Nottingham Health Profile (NHP) a scale for Activities of Daily Life (ADL) a Symptom Check List (SCL-90-R), and the Center of Epidemiology and Statistics Depression Scale (CES-D), all for self rating, as well as the indices of Spitzer and Karnofsky for foreign rating of life quality. Apart from the early postoperative period in both groups there was significant and persistant improvement in quality of life already three months after transplantation. In some dimensions, patients after kidney transplantation presented even lower trouble scores than a population sample. In addition, semistructured interviews showed clearly the need for psychotherapeutic support to guarantee the success for specific cases. The present investigation demonstrates, that systematic registration of the patients perception of illness and treatment is possible even in extreme situations and leads to a differentiated evaluation of medical procedures. Thereby the study also contributes to the development of modern evaluation research according to the spirit of evidence based medicine.