A published whole-cell binding assay of 3H-dexamethasone (3H-DEX) was combined with cell sedimentation analysis to investigate various factors influencing specific binding of glucocorticoids by leukemic lymphoblasts. Studies with mouse L1210 and human HL-60 cell lines revealed that glucocorticoid (GC) receptors accumulate during G1 phase of the cell cycle. In human lymphoblastic leukemia, the per cell receptor number was highest in cells in S and G2 phase and lowest in small, noncycling cells. In normal human white blood cells, GC receptor content was maximal in large lymphocytes and monocytes while no receptors were present in small lymphocytes. However, the receptor density of large lymphocytes was still 3-4 fold lower than of leukemic lymphoblasts of similar size. In L1210 cells the number of GC receptors decreased considerably in stationary cultures or following inhibition of cell cycle progression by dibutyryl cyclic AMP (dbc-AMP). Receptor content was also reduced in cells growing as ascites tumors in hosts with terminal disease. Accordingly, the receptor content in leukemic blasts appeared highly dependent on cell cycle distribution and on the proliferative status of the tumor cells. These findings may in part explain the large interpatient variation and the conflicting views regarding GC receptor content and prognosis in acute lymphoblastic leukemia.