Forty eight head and neck cancer (HNCA) patients were selected randomly and without any bias, from two main hospitals, Alkadhimya hospital and radiotherapy center in Baghdad. Also 22 of apparently healthy control subjects were underwent the same examinations and tests of this study as HNCA patients were. HNCA patients of this study were of 8 types and as following; 22 patients of CA larynx, 14 patients of nasopharyngeal CA (NPC), 6 patients of Hypopharyngeal CA, 2 patients of -tonsillar CA, and one patient of the rest which include post-pharyngeal CA, tongue CA, epiglottic CA and finally retromalar CA. We have taken into account only the first 3 types of HNCA groups because these groups had the sufficient number of patients that could be used in the statistical analysis. Some of HNCA patients were examined at the pre-malignant phases of the disease and they were classified into the category of their final diagnosis that was achieved many months later on. The work of this study was an immunological and serological study was focused on NPC patients and in comparison with other HNCA types, -regarding especially the relationship between Epstein Barr virus (EBV) with NPC. Three main lines of work were used in this study that include: (1) Enzyme-linked immunosorbent assay (ELISA) test which was applied on- all HNGApatients-and-HG group, in order to measure anti-EBV-antibodies in the sera of them.' Two ELISA kits were used for this purpose; the first one was designed for detecting anti-EBV serum IgG antibodies, and the second one was designed for detecting anti-EBV serum and saliva IgA antibodies. (2) Peripheral blood lymphocytes (PEL) CD markering was applied on the frozen and fixed isolated PEL slides of all HNCA patients and HC group. By using direct imniunofluorescence test. The monoclonal antibodies were used were anti-CD3, anti-CD4, anti-CD8 and anti-CD21. (3) In vitro mononuclear cells mitogenic stimulation by using microculture tetrazolium assay (MTT) test which was applied on the freshly isolated PEL of HNCA patients and HC group. The mitogens were Concanavalin A (Con A) as a control positive, S2-complex and Pneumo-23 vaccine as the test agents. The purpose of the MTT use in this study was to determine the CMI level of different HNCA patients in comparison with each other and with HC group. The second purpose of MTT was to evaluate the immunostimulatory effect of Pneumo-23 vaccine in vitro and in comparison with S2- complex, The most important findings of this study were as following: Increasing age, sex ratio of male predominance , heavy smoking, alcohol intake are important risk factors for HNCA patients especially for NPC patients. While positive family history of the disease is a risk factor of all HNCA patients except for NPC patients. South of Iraq has shown the highest number of HNCA patients except for NPC patients that come mainly from the north of Iraq. NPC patients only showed a strong relationship with EBV as a causative agent. This has been achieved by the detection of a very high anti-EBV serum IgG level in NPC patients by ELISA test, which is far higher than level in HC group. While other HNCA groups have not shown such a high level of EBV S.IgG and were not different from that of HG group. In addition to that NPC patients were the only group that showed a sero-positive ELISA readings of anti-EBV serum IgA. No saliva EBV antibodies were detected at all. Pre-malignant phases of NPC showed a similar EBV antibodies profile to definitely diagnosed NPC patients, which is an important feature that could be used in the early diagnosis of NPC at pre-malignant phases. HNCA patients have shown a remarkable lowering in CD3+, CD4+, CD8+ and CD21+ cells in comparison with HC group. NPC patients had the highest percentages of PBL subsets among HNCA patients but they had the lowest CD4/CD8 ratio. All HNCA patients have shown a suppressed CMI level . in comparison with HC group by MTT assay. NPC patients have shown the lowest CMI level among HhCA. It has been found that CD8+ cells is the main population that controls CD4/CD8 ratio which is inversely related to it. NPC patients had the highest CD8+ cells population among HNCA patients , consequently, the lowest CD4/CD8 ratio and the lowest CMI level or in another words NPC group has the highest immune suppression among HNCA patients.