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 of the atlas traces the developments in this field chronologically, summarizes the available literature and presents the current situation in the light of the most recent studies in this field. The photographs were selected to illustrate the spectrum of surface morphology of the different cell types obtained from normal individuals and patients with disease states. Hopefully, the atlas will serve as a guide for future studies and as an illustration of what SEM has to offer in providing details of surface architecture.