In this work, the authors studied the morphology of the axillary and mediastinal lymph nodes and their efferent branches in the white rat (Rattus norvegicus). The main characteristics observed were: The presence of two groups of axillary lymph nodes, one in the lateral and the other in the medial portion, and the presence of two groups of mediastinal lymph nodes, one being ventro-lateral and the other dorsoventral relating to cranial precava veins. Usually, in both sides, there is a lymphatic plexus dorsally to the jugulosubclavian angle, formed by reunion of internal jugular and subclavian trunks and the thoracic duct (to the left) or the right lymphatic trunk (to the right). From this plexus, one or two branches run off and flow into the venous jugulosubclavian angle. The subclavian trunk begins in the medial axillar lymph nodes and joins to the lymphatic plexus at the internal jugular trunk or at the thoracic duct or yet at the right lymphatic trunk according to the site, and finally it may link itself directly to the venous system. The mediastinal lymph nodes at the right side send branches forming the right lymphatic trunk and branches adhering to the lymphatic plexus; the left lymph nodes join to the plexus or the thoracic duct.