BACKGROUND Description of the patients admitted in the general Internal Medicine (IM) departments of the Public Health System in Andalusia (Spain) (PHSA) during 2002. PATIENTS AND METHODS It is an analysis of the Minimum Basic Set of Data (MBSD) and its management by the Diagnostic Related Groups (DRG) of admission episodes in Andalusian public hospitals. We divided the hospitals into group 1: more than 600 beds; group 2: between 200 and 600 beds, and group 3: less than 200 beds. RESULTS IM services discharged 80,514 patients (total in PHSA, 558,114); 25.9%, 29.6% and 44.5% from groups 1, 2 y 3, respectively; 87.4% were admitted from the emergency room. Gross mortality rate was 10.23%. Average age was 72 years, 8 years more than in the other medical departments. Mean diagnosis per episode was 5.4. The most frequent pathologies (33%) were chronic obstructive pulmonary disease, congestive heart failure, brain stroke and coronary heart disease. Adjusted length of stay was 9.35 days, this being somewhat longer in big hospitals. Mean weight of the episodes (DRG weight) of IM services was 20% higher than the mean of the rest and it accumulates 18.02% of the total weight. Real hours of outpatient clinics was 5.45% of the total. CONCLUSIONS The activity of the general IM services is very high in relative and absolute terms. Higher age and the multiple pathologies are typical characteristics of IM patients in Andalusia. Author claim it is very important to be careful with the clinical and administrative records. Interventions on prevalent diseases in IM services may produce positive and valuable results due to their high volume.