A comparison between neoplastic and nonneoplastic lymphoid cell nuclei within germinal centers of nodular lymphomas and of reactive follicular hyperplasias has been carried out with the help of a semiautomated image analyzer by measuring nuclear area, by assessing the presence or absence of invaginations, and by defining the form of the invagination. Nuclear areas are larger in lymphomas, where the invagination, if present, decreases in depth and increases in angle as the value of nuclear area becomes greater. Nuclei with such a large area and shallow invaginations are not present within the nonneoplastic germinal centers. Moreover, no correspondence has been found between neoplastic and nonneoplastic nuclei with regard to the form of the invagination, that is, its symmetry and angle. Therefore, it is possible to argue that the neoplastic nuclei in nodular lymphomas are different from the nuclei found in the sequential pathway of reactive germinal centers.