The aim of the study was to investigate factors of significance for readmission of patients in a department of internal medicine. The study was based on hospital computerized data files. All admissions from the 1st of January to the 31st of December 1995 were included. During that period the department had 6061 admissions of 4152 patients. The readmission rate was 1.46. All patients were followed three months after discharge. Within that period 1119 (27%) of the patients were readmitted. A high frequency of readmission was especially found within the first ten days after discharge. Length of stay in hospital did not influence readmission rate. Women, patients in the age group 71-90 years and patients with chronic diseases were more likely to be readmitted. The demonstrated factors relating to a high readmission rate are difficult to influence. A prospective study including the primary health care system and a clinical evaluation of the patients is needed to examine causes of the high number of readmission within the first ten days after discharge.