Avicenna is a medical decision-support system which acts on a set of symptoms to produce a ranked list of diagnoses which might explain (or be associated with) those symptoms. Avicenna provides justification for why (and to what amount) each of these diagnoses might be considered, suggests what further clinical information would be useful to collect for each diagnosis, and calculates how much the inhibited symptoms would exclude for each of the specific diagnoses. Avicenna does not offer definitive medical consultation and should not be used as a substitute for physician diagnostic decision making. Avicenna has the characteristics of both an electronic medical textbook and a medical reference system. In the role of a medical textbook, Avicenna can provide a comprehensive description of over 2000 different disorders, emphasizing the signs and symptoms that occur in each disorder, the etiology, the pathology, and the prognosis. In addition, Avicenna can provide a list of disorders which should be considered for any one of over 1000 different clinical findings. Avicenna is owned by Pezeshkyar Pars Biomedical Co.