The systemic corticoid effects of butyl 6alpha-fluoro-11beta-hydroxy-16alpha-methyl-3,20-dioxo-1,4-regnadien-21-oate (fluocortin butylester, Vaspit) in the form of 0.75% fluocortin butylester cream were tested under conditions which permit maximum absorption of the active principle. Over 8 days 40 g cream daily were applied to the entire body surface of 6 subjects and the trunk, thighs and upper arms covered with polythene foil. The plasma cortisol levels, elimination of free cortisol in the 24-h urine and eosinophilic leucocytes were compared intraindividually with the values before and three days after treatment. In addition 6 further subjects were treated with 0.1% hydrocortisone-17-butyrate cream, a preparation considered to have little systemic action. Fluocortin butylester showed no systemic corticoid effects. Cortisol secretion and eosinophilic leucocytes remained unaffected. In contrast the inhibiting effect of hydrocortisone-17-butyrate was evident in all parameters, especially in the morning plasma cortisol values. Under treatment with hydrocortisone-17-butyrate these dropped from 361 to 11 nmol/l. Under occlusion treatment with fluocortin butyl they remained constant (357 before, 320 nmol/l after treatment). The relevance of the method of examination is discussed.