We evaluated 21 maintenance hemodialysis (MHD) patients and 23 healthy control subjects quantitatively for levels of peripheral blood T-cells. Mononuclear cells isolated from peripheral blood by the Ficoll-Hypaque gradient technic were used to determine the percentage of T-cells that formed E-rosettes (%RFC) in each group. Total blood lymphocytes were also determined for each group and the results were compared. The absolute number of lymphocytes/cu mm for 21 MHD patients averaged 1,737 +/- 112 SE and the mean %RFC was 70.0 +/- 1.15 SE; comparable values for 23 normal controls were 2,081 +/- 83 and 60.2 +/- 1.01, respectively. Although MHD patients had significantly lower average values for number of lymphocytes/cu mm (t = 2.490, P less than .02), the mean value of %RFC for MHD patients was significantly higher than that of normal controls (t = 6.118, P less than .001). The data indicate that MHD patients are lymphopenic but have a significantly higher %RFC (T-cells) than do normal subjects. Based on this finding, we hypothesize that there is selective depletion of a specific subpopulation of lymphocytes in MHD patients.