We studied the mineralocorticoid pattern in 4 patients with 17OHD during long-term glucocorticoid treatment. We observed reduction of BP, normalization of K levels, a gradual increase in PRA and in urinary Aldosterone (ALDO); a normal response of plasma ALDO to ACTH and to angiotensin II was present only in one case. We observed a prompt decrease of mineralocorticoid hormones, normalized by long-term therapy only in one case. Discontinuation of treatment induced an increase of ALDO that became suppressed in late off-treatment. Thus, glucocorticoid treatment decreases abnormal steroid levels and activates zona glomerulosa (ZG) function, even if it may take years for ALDO to normalize. Brief discontinuation of therapy induces a surge in ALDO levels, revealing no biosynthetic defect in ZG, while in late off-treatment mineralocorticoids seem to come exclusively from zona fasciculata.