Long stay is a new type of hospital admission geared to internal medicine patients requiring long-term stays in hospital and prolonged treatment for the purposes of stabilization or clinical rehabilitation. Given the lack of specific experience, we monitored the progress of a Long-Stay Unit with the aim to estimate the clinical and organizational impact. We studied 263 patients (59.3% females, 40.7% males; mean age 76.3 +/- 11.5 years, 42.2% all in their late eighties) coming from medical wards (75%) and from surgical wards (25%). The clinical complexity was prospectively estimated by a form divided into 3 sections: the first part was filled out at the time of transfer, the second part at set intervals throughout the period and the third at the end of the stay. Mean length of stay for medical patients was 33.2 days, for surgical patients 28.6 days (NS). Main transfer diagnosis: 50% of the patients fell into two diagnostic groups: malignant neoplasm (33.1%) and cerebral ictus (17.5%). Some data evidenced remarkable clinical complexity: 93.9% of the patients had one or more secondary diagnoses; when initially admitted 89.4% already presented with complications or serious outcomes; while in the Long-Stay Unit 83.3% required medical treatment and extensive nursing care; 87.1% had further major complications; 56.3% was totally dependent; 42.6% was totally bedridden and 35.4% died. In conclusion, the majority of long-stay patients in a medium-to-large polyclinic hospital present with several concomitant diseases, with extremely invalidating complaints, characterized over the short-to-mid term by serious clinical complications. They require a great deal of competent medical/nursing care as well as highly qualified internal medicine specialists.