A comparison of the template capacities of purified chromatin from the kidney cortices of control and aldosterone-treated rats, which had been previously bilaterally adrenalectomized, indicated that in the presence of added DNA-dependent RNA polymerase, the capacities of the purified chromatins to act as templates for RNA synthesis were equal 90 min after hormone injection.Since 1.2% of the guanine–cytosine nucleotide pairs of the chromatin from the control rats bound actinomycin-D-14C while 0.6% of the guanine–cytosine nucleotide pairs of the chromatin from the hormone-treated animals did so, it is possible that the physical or chemical state of the chromatin had changed with aldosterone treatment.