OBJECTIVE The Tromsø Medical Department Health Benefit Study was designed to estimate health gains from admissions to a department of internal medicine. We have previously reported that the hospital stays had no effect on the life expectancy of 61% of the patients. However, it has been claimed that modern medicine has a greater effect on quality of life (QoL) than on life expectancy. The aim of the present study was to investigate this issue by estimating gains in QoL for patients admitted to a department of internal medicine. METHODS The time trade-off method (TTO) was used for assessing QoL gain from consecutive admissions during a 6-week period. The assessments were made by one of two expert panels, each consisting of an internist, a surgeon and a general practitioner, on the basis of summaries of all relevant clinical information about the patients. Short-term improvements in QoL during the stay or shortly after discharge were scored on an ordinal scale. RESULTS Of the admitted patients, 41% had gains in QoL measured with the TTO (mean gain = 0.06; 95% confidence interval = 0.05-0.07; n = 422), and eight of these had gains equal to or greater than 0.50. Another 40% had gains in health-related short-term QoL measured with the ordinal scale. In a multivariate linear regression analysis, emergency admissions, high age and the disease categories 'endocrinological diseases' and 'pneumonia and influenza', were associated with higher gain, and 'undiagnosed symptoms' and 'cerebrovascular diseases' with lower gain. CONCLUSIONS As judged by the expert panels, the investigated department of internal medicine was effective in improving the QoL of 81% of the admitted patients. Whilst most of the patients achieved small gains, a minority had gains in QoL corresponding to the treatment of life-threatening diseases.