An experimental study concerning the effect of acute and chronic irritation on corneocytes was made in relation to cell number, size, and shape. Corneocytes from skin acutely irritated with a rough towel differed from those of normal skin: There was about a 60% decrease in the count and the corneocytes were 14% smaller in size on day 1 of the experiment. These parameters became normal in count and size after 10 days and 5 days, respectively. Concerning the morphological classification of cell outlines, there was no significant difference between the experimental and control groups except for slightly increased numbers of irregular cells in the experimental group. For the chronic irritation study, subjects were scrub nurses who had worked in the operating room for more than 3 years; ward nurses were used as a control group. Corneocytes from scrub nurses differed from those of the nonirritated skin of ward nurses; the number was twice as high on day 1 of the experiment. Two and four days later, the cell number markedly decreased and was similar to that in the control group. Throughout the experimental period, the surface of the corneocytes was 15% smaller in the experimental group than in the control group. There was no significant difference between the two groups with regard to corneocyte morphology.