data from the mortality information system (sim in portuguese) are the main source of information on mortality in brazil, in spite of frequent inconsistencies. one of the main drawbacks in the generation of reliable data on mortality in brazil is due to the difficulties faced by doctors for the correct completion of the death certificate (do in portuguese). this standard document feeds data into the sim. the paper presents a support tool for the correct completion of the do, represented by an application ontology, developed on the field of mortality as. the tool was made available to physicians of city department of health and welfare of belo horizonte (smsa-bh in portuguese) via a website, containing the terms defined in the ontology and their relationships, arranged in a taxonomic structure. the proposed solution has the main objective of assisting doctors in their task of registering the occurred deaths, by means of the correct way of filling out the do.