The diameters of the cell nuclei were measured in imprint preparations of eight tonsils and 28 lymph nodes, each specimen being from a separate patient. The lymph nodes were from cases of Hodgkin's disease (HD), non-Hodgkin's lymphoma (NHL), and reactive benign states. The nuclear diameters were measured by means of an image-analysing device, the Zeiss Microvideomat. For accurate measurements, the cells had to be well separated, and tissue sections could not be used because the close juxtaposition of nuclei gave erroneous readings. However, cell imprints proved suitable. The results show that the mean nuclear diameters for the HD, NHL, and reactive groups differ and show a considerable scatter. However, the distributions for the NHL and reactive nodes are sufficiently different to suggest that the method may have diagnostic value for the former.