A method for focal dialysis of the adrenal cortex is introduced allowing determination of adrenal steroid local release rates in conscious, freely moving rats. Etomidate, an anaesthetic drug known to interfere with adrenal steroid synthesis, blocks not only corticosterone but also aldosterone and, to a lesser degree, progesterone release. Intra-adrenal application of the drug via the dialysis system for a defined time resulted in low release rates of corticosterone without inducing sedation of the animals or even anaesthesia. Remaining low steroid concentrations during the next 5 h after cessation of the dialysis with drug-containing medium indicate that the inhibition of steroid synthesis lasted for several hours. It is concluded that the inhibitory effect of etomidate on steroid biosynthesis can be explained on the basis of an interaction of the drug with adrenocortical enzymes without the involvement of hypothalamic or hypophyseal mechanisms.