Clinical, serological and lymphocyte studies were done on 435 patients with biopsy proved anaplastic nasopharyngeal carcinoma (NPC) in various clinical status, at the National Taiwan University Hospital, from January 1980 through June 1983. Studies on 134 normal control were also done. Using immunofluorescent antibody method, seropsitive rates of the antibody titers against viral capsid antigens (VCA) and early antigens (EA) of Epstein-Barr (EB) virus were 70.8%-100% for anti-VCA/IgG titers (greater than or equal to 1:640), 81.0%-100% for anti-VCA/IgA titers (greater than or equal to 1:40), 66.7%-93.8% for anti-EA/IgG titers (greater than or equal to 1:160), and 40.0%-87.5% for anti-EA/IgA titers (greater than or equal to 1:40) in NPC patients with disease. They decreased to 10.5%-21.7% in remission patients. In contrast, they were less than 5% in the control. Mean total serum IgG and IgA levels were moderately increased to around 1,500 mg/dl and 300 mg/dl respectively, in all patients. The increase was most remarkable in patients with liver metastases. In control the values were 1,211 mg/dl and 223 mg/dl, respectively. Mean serum IgM, C3 and C4 amounts of NPC patients were not significantly different from those of the normal control, the latter were 129, 80.3 and 43.2 mg/dl, respectively. Serum acid phosphatase and calcium levels of NPC patients were all in the normal range of 0.1-2.0 BU/ml and 2.0-3.0 mmol/dl, respectively. Serum GOT, GPT, alkaline phosphatase, lactate dehydrogenase and mucoprotein were elevated either alone or in combination in some patients before treatment, in many patients with neck recurrence or distant metastases, but in all patients with liver metastases. Using monoclonal antibodies (Ortho Inc., U.S.A.) to define lymphocyte subsets, B lymphocytes comprised about 12% and T lymphocytes about 60% in the patients, whereas they were 11.9% and 73.1% in the control. The helper/suppressor ratio was 1.7 in the control and about 1.0 in NPC patients, and was only 0.8 in remission patients. The lack of correlation between the seropositive rates of anti-VCA antibodies and the helper/suppressor ratio might indicate different manifestations of humoral and cellular immunity in patients with NPC.