OBJECTIVE: To describe the characteristics of the consultations carried out by surgical services to an Internal Medicine service and to determine what factors influence the prognosis of these patients. METHODS: A prospective study of the consultations carried out by the surgical services of a 540-bed hospital to an Internal Medicine service. Analyzed variables were: age, sex, service of reference, reason for consultation, medical and admission diagnoses done during the admission, and clinical evolution. RESULTS: In the study 453 interconsultations were included, corresponding to 0.96 new interconsultations by working day and to 4.05 interconsultations per every 100 admissions in surgical services during the period study. The reasons for the more common consultations were dyspnea, fever, electrolytic and metabolic disorders, assessment of multiple conditions and acute confusional syndrome. Two or more diagnoses were carried out in 257 patients (56.7%). The average number of visits carried out by patient was 3.9 +/- 3.9. The average hospital stay in the study group was 28 +/- 33.05 days, while the average hospital stay of patients admitted in the surgical services during the same period was 11.6 days. Fifty patients (11%) had died at the time of the "medical discharge", and this percentage amounted to 20.5% (93 cases) upon considering the end of the hospital admission, compared with the global mortality of 3.7% registered during that period in the surgical services. The number of medical diagnoses and the age were independent predictors of mortality in the multivariate analysis. CONCLUSIONS: The interconsultations of the surgical services to an Internal Medicine service imply an important workload. The patients are complex from the medical standpoint. The average hospital stay and mortality of these patients are different from that of the patients cared in surgical services.