A quantitative method using glass capillary column gas-liquid chromatography (GLC) has been established for the analysis of corticosteroids in small biological samples such as a few mililiters of medium from steroidogenic cultured cells. The steroid extract is separated in three main thin-layer chromatographic fractions. The steroids assayed in these fractions are: less polar fraction (C 21O 2 steroids), 20 a-dihydroprogesterone, pregnenolone and 20 a-dihydro-pregnenolone; intermediate fraction (C 21O 3 steroids), deoxycorticosterone, 11-oxo- and several hydroxy-20 a-dihydroprogesterones; corticosteroid fraction (C 21O 4 steroids), corticosterone and 18-hydroxydeoxycorticosterone. The method has been assessed by characterizing the steroid structures and checking the purity of GLC effuents through direct coupling of the capillary column to the electron-impact or chemical-ionization source of a computerized mass spectrometer. Applications to the quantitative evaluation of the endocrinological status of newborn rat adrenocortical cell cultures under various conditions of development, hormonal stimulation or specific inhibition by drugs are described.