Objective: to describe the clinical case of a rare heart disease-left ventricular non-compaction. Materials and methods. Patient G., 1948, was hospitalized in connection with complaints of fluctuations in blood pressure, heart failure, discomfort in the heart, dizziness, headaches. The patient underwent the following general examination: general and biochemical blood tests, electrocardiography, Holter ECG monitoring, treadmill test, echocardiography, color duplex scanning of neck vessels, ultrasound of the thyroid and kidneys, chest X-ray. Results. Based on the history, complaints, clinical picture of the disease, objective and instrumental examination data, a clinical diagnosis was made: left ventricular non-compaction. One of the main diagnostic methods that allowed to verify the diagnosis was echocardiographic study: the structure of the myocardium of the lower-apical section of a two-layered one, with the presence of a noncompact layer (with intertabercular breaks), in relation to the compact as 2:1; a small extension of the left atrium; small hypokinesia in the lower-upper segment of the LV, without a decrease in the LVEF (PV = 73 %). Conclusion. This clinical case is interesting because the disease, concealed under the guise of rheumacarditis in an era when ultrasonic methods of examining the heart were not available in clinical practice, has now been diagnosed in the conduct of a reference echocardiographic study. Despite the fact that this disease belongs to rare nosology, it can occur in any age group and can often be asymptomatic.