A method is proposed for the quantitative determination of diagnostically important corticosteroids (cortisol, cortisone, corticosterone, 11-deoxycorticosterone, and 11-deoxycortisol) in blood serum and urine (cortisol and cortisone) in an isocratic mode of reversed-phase high-performance liquid chromatography (RP HPLC) with the use of β-cyclodextrin as a component of the mobile phase (CH ₃CN : H ₂O). Biological fluids (blood serum and urine) from a group of healthy donors and patients with various endocrine diseases (Cushing's syndrome, congenital adrenal hyperplasia, aldosteroma, and adrenal cortex carcinoma) were examined, and characteristic chromatographic steroid profiles were obtained for these disturbances.