We studied the circadian rhythm and the response of the hypothalamic-pituitary-adrenal (HPA) axis to ovine corticotrophin releasing hormone (oCRH) stimulation and dexamethasone suppression in 32 children with grade II-III marasmus. Children were studied prior to and after nutritional rehabilitation. Mean baseline plasma cortisol concentrations were elevated at admission and decreased significantly after nutritional rehabilitation. Mean +/- SEM plasma cortisol response to oCRH increased from a basal of 480 +/- 41 to a peak of 582 +/- 58 nmol/l at the time of admission, and from a basal of 234 +/- 27 to a peak of 532 +/- 41 nmol/l after caloric rehabilitation. Dexamethasone suppression in the malnourished group was associated with a decrease in the mean +/- SEM basal plasma cortisol concentration from 397 +/- 44 to 171 +/- 44 nmol/l. After caloric rehabilitation, basal cortisol levels decreased from 259 +/- 27 to 22 +/- 5 nmol/l following dexamethasone. Our results support the concept that malnutrition is associated with decreased responsiveness to oCRH and incomplete dexamethasone suppression, and that these abnormalities are restored after nutritional rehabilitation.