This chapter discusses the lymph nodes and their classifications such as the cervical lymph nodes, axillary lymph nodes, inguinal lymph nodes and supraclavicular lymph nodes. It also discusses different diseases related to the lymph nodes in a human body, and the process to examine and determine their causes as well as the signs and symptoms associated with them. Lymph nodes are the sources of the lymph and lymphocytes, an agranulocytic leukocyte that normally makes up a quarter of the white blood cell count but increases in the presence of infection. Lymph node-related ailments, such as acute lymphadenitis can occur at any age, while tubercular lymphadenopathy, Hodgkin’s disease and syphilis are commonly seen in young adults. Lymphomas, which have a bimodal distribution, are seen among the youth, who may develop it later in the old age too. Carcinomas are more often seen in old age. The causes of generalized lymphadenopathy include infections, sexually transmitted diseases, collagen vascular diseases and neoplastic diseases such as Hodgkin’s lymphoma, lymphosarcoma and Myelocytic leukemia.