Cytological examination of smears or imprints of diffuse non-leukaemic lymphomata gives more details of the morphological aspects of the cells than does histological examination. It enables us to distinguish (a) prolymphocytic (but not lymphocytic), (b) lymphoblastic or lymphoblastoid and immunoblastic lymphosarcomata. It helps to diagnose so-called reticulosarcomata from carcinomata and to distinguish two types: (a) cytic and (b) blastic, but it makes us suspicious about the nature of the latter. Light microscopy shows the cells of the blastic type resemble transformed lymphocytes (immunoblasts) more than reticulum cells. Electron microscopy shows many polyribosomes, which enhances the suspicion that some so-called "reticulosarcomata" could be immunoblastic lymphosarcomata.