EN
The paper presents methods of Fuzzy Set Theory which can be a helpful key to medical diagnosis on the basis of symptoms as well as to the differentiating the effectiveness of action of drugs (metronidazole, tinidazole and omidazole) in trichomoniasis. The relationship between patients and symptoms, symptoms and diagnoses or patients and diagnoses is considered as a fuzzy relation. A max-min composite fuzzy relation is a mathematical apparatus for finding the diagnoses such as: trichomoniasis, mycoses or bacterial infection. The solution of the other problem is based determining an eigen fuzzy set, associated with a given fuzzy relation, which can help to predict the theoretical maximal and minimal levels of recovery.