1. 1. Hydrocortisone increase in vivo incorporation of [14C]glucose into fetal liver glycogen in the last days of gestation, whereas in glucagon-treated fetuses, a slight decrease in the incorporation rate was found. 2. 2. Hydrocortisone increases total synthetase activity as that of synthetase a but was without effect on fetal liver glycogen phosphorylase. 3. 3. Glucagon causes a slight increase in phosphorylase a activity on days 19-21, and was without effect on the activities of synthetase a and total synthetase. 4. 4. Dibutyryl cyclic AMP had no effect on the key enzymes of glycogen metabolism 1 h after injection in utero, whereas after 6 h an increase in phosphorylase a activity was found without any change in synthetase a activity.