This paper presents a computerised information system for the characterisation and analysis of the hospital admission flow of patients. Based on administrative data made available by the Ministry of Health of Brazil (DATASUS-MS), the system allows the representation of patients' flow from residence to hospital, as well as information on performed medical procedures, diagnoses and other patient and hospital characteristics. Residences are represented in terms of their postal codes and admission diagnosis according to the ICD-10 classification. The system has a flexible and simple geographic coordinates input module, and can be used even when no standard coordinates system (e.g., Mercator) are available. It provides two types of graphical representation: 'static' (concerning characteristics of a hospital or geographical area) and 'dynamic' (residence to hospital flow). Its use is exemplified with a geographical representation of access to ultra-sound exams in selected hospitals in the city of Rio de Janeiro, Brazil, July 1998. In conclusion, the system seems a powerful instrument for health needs identification and planning, as well as for quality assessment and for the generation of information useful for epidemiological research.