The world data show a large number of people with illness anxiety disorder (hypochondriasis) among the population all over the world. Russia is no exception: hypochondriacal patients often seek dental care. A dentist should be able to identify this category of patients. As a rule, these patients "know everything": their diagnosis and the most modern and effective methods of treatment. They are truly literate people. Their medical literacy is the result of watching popular shows, reading articles in trendy magazines and medical websites. Frequently, these patients are not emotionally stable; they have been stressed for a long time, or are undergoing long-term hormone therapy. Identifying these patients is the key to the successful practice. This article describes an interesting clinical case of the patient, who was treated for 2 months by 5 different specialists and took strong medications. During treatment her condition only worsened: allergic reaction developed to medications, with lesion of mucous membrane of oral cavity. Her reluctance to stop taking medications, insistence on consulting a dentist-oncologist alerted the attending doctor. Analysis of medical history revealed that the patient had experienced severe stress in the recent past and was currently undergoing a course of hormonal corrective therapy. A clinical psychologist confirmed the dentist's suggestion that the patient had hypochondriacal disorder. Patients with hypochondria - who are they? How to recognize them? If you meet such patients at a dental appointment, how you should communicate with them? How to treat them? A good result is achieved by establishing contact with the patients and their family and friends. Sometimes it is impossible to do without the help of a clinical psychologist. Only this specialist can definitively decide: does the patient have hypochondriacal disorder or not? If necessary, the clinical psychologist provides special treatment. The probability of a favorable outcome with this approach is high.