Percutaneous absorption of hydrocortisone was studied in 18 young adults during and after the acute phase of atopic dermatitis using the direct hydrocortisone absorption test. In the acute phase the post-application increase in serum cortisol concentration ranged between 18 and 711 nmol/l (median 125 nmol/l). In remission the increase in serum cortisol ranged between 0 and 114 nmol/l (median 16 nmol/l), which was significantly lower than the rise in the acute phase. In the acute phase of dermatitis, topical hydrocortisone treatment has both a local and a systemic effect, due to percutaneous absorption.