We have analyzed the kinetics of salivary cortisol (F) and 17-hydoxyprogesterone (17OHP) after a single oral administration of hydrocortisone (HC; 10 mg; 0700 h) in healthy male volunteers (n = 10; 18-29 yr) and in patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (males, n = 7; females, n = 3; 8.5-20.4 yr). The HC doses, related to body surface area, ranged from 6.3-9.2 mg/m(2) in controls and from 4.2-10.7 mg/m(2) in CAH patients. Saliva was collected over 5 h (at intervals of 15-30 min), and the steroids were measured with adapted RIAs. In healthy controls, maximal cortisol values (250.3 +/- 35.9 nmol/liter) were reached after 30 min. Values showed a monophasic decrease. A t(1/2) of 94.5 min was calculated. The proportion of the HC dose in the total area under the curve was 71.2 +/- 3.2%. For 17OHP, a monophasic decrease was found, with a minimum level of 48 +/- 27 pmol/liter after 300 min. In CAH patients the salivary steroid profiles showed individual kinetics (maximal cortisol values ranged from 107-726 nmol/liter). Here a monophasic decrease was found with a shorter t(1/2) of 56.4 min. The HC dose proportion in the area under the curve was 88.3 +/- 6%. 17OHP showed biphasic courses with a decrease to the minimum 17OHP level after 210 min at the latest and a subsequent gradual increase. Our findings of limited normalization of the adrenal cortex by oral HC administration underlines the necessity of optimizing therapy control and indicates the usefulness of kinetic studies for the judgement of therapy in CAH patients.