A simultaneous radioimmunoassay for delta 4-androstenedione (delta 4), dehydroepiandrosterone (DHA) and 11 beta-hydroxyandrostenedione (11 beta OH delta 4) in plasma is described. This involved preparing first an anti-11 beta-hydroxyandrostenedione-3-0-carboxymethyl oxime/BSA antiserum which binds both delta 4 and 11 beta OH delta 4, and an anti-dehydrosterone-7-0-carboxymethyl oxime/BSA antiserum. A chromatographic step using celite minicolumns separates these three steroids. The method was applied to the measurement of the plasma basal values of these three androgens in control subjects. Mean concentrations (ng/ml) of delta 4, DHA and 11 beta OH delta 4 were respecstively 1.35, 6.63 and 3.13 in males; 1.35, 6.65 and 2.59 in premenopausal females; 0.46, 1.53 and 1.38 in post-menopausal females, and 0.39, 0.73 and 1.78 in children 1--6 years of age. Dynamic tests were also carried out: ACTH stimulation was found to increase delta 4, DHA and 11 beta OH delta 4. Dexamethasone had a reverse effect causing a 50% diminution in delta 4 levels, a marked decrease in DHA levels, and a 90% decrease in 11 beta OH delta 4 levels. Metyrapone test was found to produce a 223% increase in delta 4 levels, a 196% increase in DHA levels, and a decrease of more than 90% in the 11 beta OH delta 4 levels. Estroprogestative drug treatment was accompanied by a decrease of not only delta 4, but also of DHA and 11 beta OH delta 4. Preliminary clinical results concerning these steroids show a parallel increase or decrease of delta 4 and 11 beta OH delta 4 in adrenal pathology. In ovarian hyperandrogeny, delta 4 is increased and 11 beta OH delta 4 is unchanged.