Recent extensive development of thoracic surgery meets the need to treat elderly patients with a wide variety of pathophysiologic alterations, even if they require continuous medical assistance and high technologic support. Methods in providing such care are still limited by imprecision in evaluation of results; in this setting, a severity of disease classification system is essential to estimate the pretreatment risk of death of elder or chronically ill patients, the appropriate indication to surgical treatments, and the prediction of outcome. We tested hospital admission characteristics and hospital mortality on 59 consecutive high-risk patients from our Surgical Department using the APACHE II severity of disease classification system. Predicted mortality rate for the high-risk patients was 12.44 percent and total mortality ratio (actual deaths/predicted deaths) was 0.94. The APACHE II scoring system showed good correct classification rate, sensitivity, and specificity.