The scanning electron microscope has been used to examine scales taken from the scalp of 3 patients with pityriasis amiantacea alone, 3 psoriatic patients with pityriasis amiantacea and one patient with both atopic dermatitis and pityriasis amiantacea. Samples from 2 patients were additionally studied by different fixation techniques and in the frozen hydrated state, but no cementing of the scales could be observed. There was no evidence of an infective agent.