The scanning electron microscope (SEM) has been used with increasing frequency in recent years to study the surface mor phology of normal, transformed and malignant leukocytes. Since the original reports on critical point-dried lymphocytes published in 1973, results of other studies using improved methods have been reported giving rise to some controversy in this field and this is discussed in the text of the atlas. Advances in preparatory techniques recorded during the past 3 years have also contributed much to a better understanding of cell surface phenomena as seen under the SEM. The text...