Highly compressed disc-shaped tablets of testosterone and its esters, of estriol, and of estradiol and its esters were absorbed in [male] rats at a very steady rate. The amts. ab-sorbed did not fall as rapidly as would be expected theoretically, so that a fairly constant dosage could be maintained for several wks. or mos. Variation in this dosage was small, from tablet to tablet of the same substance. Diethylstilbestrol and its diesters were less regularly absorbed from tablets than were the steroid hormones, but variation was still not excessive, usually within [plus or minus]25% of the mean of a group. Esterification decreased the rate of absorption, with the exception of estradiol dipropionate, which was absorbed rather more rapidly than free estradiol. A wide range of dosage was thus available. In some cases, notably those of diethylstilbestrol and methyl testosterone, the tablets were liable suddenly to disintegrate, but this did not occur with the majority of compounds.