The aim of this work is to present a detection system of reportable diseases among patients attending a teaching hospital. Since January 1988, based on daily data obtained from the Admissions Department of Hospital Clínic of Barcelona (HCP) (emergency department visits and hospital admissions and discharges), the Preventive Medicine Unit identifies every day those diseases considered as reportable by the Department of Health of Catalonia, Spain. Reported cases from HCP during the 1988-1991 period were compared to cases reported from HCP in 1987, as well to the corresponding cases in the remaining hospitals of Barcelona. Between 1987 and 1988 there was a 245% increase in the reporting of Individualized Reportable Diseases and of 4345% for Numeric Reportable Diseases. The increased notification has also been shown for the most frequent Individualized Reportable Diseases: 364% for hepatitis, 195% for meningococcal infection and 233% for pulmonary tuberculosis. This system is an approach to the introduction, development and perfection of the detection process, in order to improve reporting levels in the hospital, contributing to strengthen the epidemiologic surveillance system in the community.