1. Some of the effects of stress, fasting and ACTH injections in pregnant ewes were investigated.
2. A 6-day fast produced a relatively mild hypoglycaemia and hyperketonaemia without inducing pregnancy toxaemia.
3. Stress of transport produced an immediate slight rise in plasma cortisol; 4 hr. later the plasma cortisol had returned to the pre-stress levels.
4. A combination of stress and fasting produced severe hypoglycaemia, hyperketonaemia and subacute pregnancy toxaemia, but there was no increase in plasma cortisol levels.
5. Daily injections of ACTH resulted in a fourfold increase in plasma cortisol and prevented the development of hypoglycaemia, severe hyperketonaemia, and pregnancy toxaemia in pregnant ewes subjected to stress and fasting.
6. Changes in plasma concentrations of NEFA, urea, proteins, catecholamines and insulin were also investigated.