Attention to the topic of accessory mitral valve tissue intense in the 90s. After that, it would seem that interest began to fade, however, at present it has begun to increase again according the number of reviews found in MedLine. ‘What is the reason for the increased interest’, ‘what is the current state of art’ these questions were the background for this review. This lecture summarizes new knowledge about mitral valve accessory tissue and makes it clear that it is important to physicians in many specialties including internists.