Two patients with solitary lesions of pagetoid reticulosis are presented. A third case with disseminated lesions and similar microscopic detail is also reported. Lighg microscopic findings include an abnornal cell infiltrate confined to the epidermis and distributed diffusely in a pagetoid pattern. In ultrathin sections, the abnormal cells are seen to have an abundant cytoplasm with numerous organelles and a convoluted nucleus, often with a prominent nucleolus. The nature of the abnormal cells is discussed. The infiltrate is differentiated from that of mycosis fungoides.