Introduction: Histologically, each lobe of the thymus can be divided into a morphologically distinct cortex and medulla separated by a vascular cortico-medullary zone. Material and Methods: Out of 15 cadaver’s two males and one female cadaver showed persistent thymus. Initial sections were stained with Haematoxylin–Eosin methods. Additional sections were used for immunohistochemistry and stained for the expression of high molecular weight cytokeratin, CD3. Result: Immunohistochemistry profile had shown intensely positive immunoreaction for CD3 to lymphocytes Discussion: The involution process of thymus begins at puberty, but it is now known that the relative volume of the thymus decreases even in the mid-childhood. In our study adequate number of cortical T cells with epithelial cells were noted. Moderate affinity of high molecular weight cytokeratin to epithelial cell is seen which is suggestive of persistent of active thymus. The immunohistological findings of persistent active thymus are not only important for the better understanding of the a etiology of thymic disorders but also beneficial for better patient management and outcome.