Background: It is axiomatic that an understanding of the complex architecture of the atrial musculature should improve understanding of its activation and contraction. The left atrium possess a venous component, a vestibule and an appendage and shares the septum. The structure of the heart undergoes constant adaptation to physiologic changes in the organism. LAA is a major endocrine organ and is the main producer of ANP (atrial natriuretic peptide) in the human heart. Atrial cardiocytes of the mammalian heart contain granules which are morphologically similar to those in peptide secreting endocrine cells. The cardiocytes of LAA contain the greatest density of ANF granules found in Left Atrium and it is therefore of interest to carry out further studies on these granules.(1) Aims: Looking to the great clinical significance that is given to the morphology of LAA & its predilection as a site for thrombus formation, we’ve conducted a detailed study histologically of LAA. To investigate LAA and study the arrangement of muscle bundles, collagen fibres & connective tissue of LAA histologically (with a special stain-Van Geison’s)and these findings were co-related with that described in the literature. Material & methods: The materials for the present study were collected from the Department of Anatomy & Forensic medicine of Sri Aurobindo Medical College and Post Graduate Institute, Indore. Randomly five hearts were selected and slides of LAA from different sites (apex, inferior margin and atrio-auricular junction) were prepared by routine Histological Techniques and stained by Haematoxylin & Eosin and Van Geison’s(special stain) Conclusion: This study of its histological features is an attempt to establish the cause of various pathologies related to arrythmias. Key words: ANF (Atrial natriuretic factor), LAA(Left atrial appendage), histologically