By means of the fluorescence activated cell sorter (FACS), we analyzed the T-lymphocyte subpopulations in peripheral blood samples from 82 patients showing various clinical manifestations of psoriasis. With regard to both the absolute values of T-helper and T-suppressor cells and those of the T-helper/T-suppressor cell ratios, there were no quantitative differences between the patients (i.e. either the entire collective of classified according to the various forms of psoriasis) and the control group. We discuss the pathophysiological relevance of peripheral and in situ analyses of T-lymphocyte subpopulations