High lymphocytes do not indicate the severity of the disease, but need to be combined with clinical manifestations and other tests to make a comprehensive judgment. High lymphocytes can be seen in infectious diseases (such as viral infections), mature lymphocyte tumors, recovery from acute infectious diseases, transplantation rejection and so on. 1. Infectious diseases: mainly viral infections, such as measles, chicken pox, mumps, viral hepatitis, etc., the percentage of lymphocytes is higher than 40%. 2. Mature lymphocytic tumors: such as non-Hodgkin’s lymphoma blood routine is generally non-specific, most of the white blood cells are normal, which may be accompanied by absolute or relative increase of lymphocytes. Early stage is generalized painless progressive lymph node enlargement, with the progress of the disease, it gradually invades other organs, and the diagnosis is mainly confirmed by the pathology of lymph nodes. 3. Recovery period of acute infectious diseases: such as influenza, measles and other diseases, the percentage of lymphocytes may still be high after the clinical manifestations have improved. 4. Transplant rejection: high lymphocytes can be caused by the immunopathologic reaction between the graft and the recipient. There may be other reasons for high lymphocytes, so it is recommended to go to the hospital in time to find out the cause of the disease and carry out regular treatment as soon as possible.