Disclosed is a method for assistance with the establishment of a diagnosis of a patient, starting from at least one identified sign, and based on a computerized knowledge database including a medical ontology. The medical ontology includes: a list of signs forming a “sign” class; a list of pathological states forming a “pathological state” class; and a first set of logical relationships between the signs and the pathological states, each logical relationship establishing a correlative link between a sign and a pathological state. The method includes: a step of searching for potential pathological states, linked to at least one of the identified signs by the first set of logical relationships; and a step of identifying potential signs in which, for each potential pathological state, all of the signs linked by a correlative link to the potential pathological state are identified by the first set of logical relationships.