Cytogenetic analysis was undertaken to study oncogenesis on patients with head and neck mass. Four cases of head and neck mass revealed different pathologic diagnosis and cytogenetic analysis respectively. Case one was metastatic cancer of unknown primary which revealed various chromosomal aberrations. The characteristic findings were T(1 : 9)(q31 : q34), del(11)(q14) and del(11)(q23). Case two was lymphoepithelioma. The cell line showed simple chromosomal abnormality, and del(2)(q34) and del(15)(q23) were observed. Case three was malignant lymphoma. The chromosome number was generally tetraploid range and this finding suspect this case as advanced carcinoma. Case four was reactive hyperplasia. Reactive hyperplasia is not a real neoplasm but this case showed 50% of chromosomal aberration. Each four case had different chromosomal abnormalities respectively, therefore investigation of chromosomal abnormality through cytogenetic analysis on each mass will be helpful to understanding oncogenesis.