A 29-year-old woman with Addison's disease was hospitalized in the eighth week of pregnancy because of an Addisonian crisis. The crisis was successfully treated with physiological saline infusions, as well as hydrocortisone (25 mg/d) and fludrocortisone (0.05 mg/d). The dose of fludrocortisone had to be increased to 0.1 mg/d from the 21st week of pregnancy onwards, because hyponatraemia and hypotension had once again developed. The hydrocortisone dose was raised to 37 mg/d from the 32nd week of pregnancy onwards because of a latent hypoglycaemia and raised further to 50 mg/d from the 35th week onwards because the retardation in fetal growth had become more marked. A mature infant was delivered spontaneously on the 282d day of pregnancy. At the start of labour the patient had been given 100 mg hydrocortisone intravenously and then 50 mg at the moment of delivery. The substitution treatment was gradually reduced to the original (pre-pregnancy) dosage during the first three post-partum days.