81 untreated malignant lymphomas of the neck were classified morphologically according to the German Kiel classification and to the American classification of Rappaport and Berard and these tumors were typed immunologically as to their T- or B-cell nature. Cells from 16 of these patients were subsequently grown in tissue culture for periods up to seven months. Tissue culture cells were monitored as to spontaneous variations in the morphologic cell type and to the expression of T- or B-cell surface determinants. In addition in 10 patients sera were tested for anti-Epstein-Barr virus (EBV) antibodies. The results of these investigations were correlated with the course of the individual neoplastic disease. Significantly elevated titers against EBV antigens were detected primarily in 8 of 10 patients, mainly in lymphocytic lymphomas respective lymphoplasmacytoid immunocytomas. All such neoplasms belonged immunologically to B-cell lymphomas and were readily grown in tissue culture. The morphological cell type and the expression of B-cell determinants showed some variation during the culture period. In contrast,lymphomas of EBV-negative patients or patients with low EBV-titers grew poorly in tissue culture and remained morphologically more stabile. Immunocytologically they belonged to tumors with B- and T-cell deficiency and were classified primarily as histiocytic lymphomas and as Hodgkin's lymphomas. The clinical course in slow proliferating tumors seemed to be rather disadvantageous.