Mitral insufficiency is defined as inadequate closure of the mitral valve, allowing blood to return from the left ventricle to the left atrium in systole. MI is common in the general population with a prevalence of 1.6 to 1.7%, with an increase in incidence in the elderly. It is the second most frequent indication for heart valve surgery after aortic valve stenosis. According to the cause, MI is classified as primary or secondary. The primary is caused by a pathologically altered valve, while the secondary is caused by ventricular pathology. The mitral valve is made up of two leaflets, a fibrous annulus and a subvalvular apparatus, which is made of chordae tendinae and papillary muscles. The most common etiology of primary mitral regurgitation in developed countries is valve prolapse, while in developing countries it is rheumatic valve disease. Mitral regurgitation is classified by Carpentier into three types, based on leaflet motility. Patients with chronic MI remain asymptomatic for many years in the compensatory phase of the disease. When decompensation develops, patients are most often presented with symptoms of left-sided heart failure, dyspnea, and exercise intolerance. A characteristic auscultatory finding of MI is holosystolic murmur, best heard at the apex of the heart with radiation to the left axilla. The gold standard in the diagnosis of MI is echocardiography. Two-dimensional transthoracic and Doppler echocardiography are most commonly used. Definitive treatment of chronic MI is surgical. There are two surgical treatment options: mitral valve repair and mitral valve replacement. The gold standard of surgical treatment is mitral valve repair due to lower operative mortality, higher survival rates and fewer complications.