The presence of brain natriuretic peptide (BNP) in tissues of human adrenal glands and adrenal tumors was investigated by radioimmunoassay. Immunoreactive BNP concentrations were 0.203 ± 0.061 pmol/g wet tissue (mean ± SEM) in normal parts of adrenal glands (cortex and medulla, N = 8), 0.205 ± 0.037 pmol/g wet tissue in pheochromocytomas (N = 8), 0.230 ± 0.062 pmol/g wet tissue in aldosteronomas (N = 11) and 0.180 ± 0.054 pmol/g wet tissue in adrenocortical adenomas with Gushing's syndrome (N = 4). Sephadex G-50 superfine column chromatography and reverse-phase high-performance liquid chromatography showed that most (> 70%) of the immunoreactive BNP in the normal part of adrenal glands was eluted in the position of human BNP-32. Sephadex G-50 superfine column chromatography of immunoreactive BNP in the pheochromocytoma and aldosteronoma showed four peaks: one in the position of γ-BNP, one in the position of BNP-32, one between γ-BNP and BNP-32 and one in the smaller molecular weight region. The present study has shown that immunoreactive BNP is present both in normal human adrenal glands and in adrenal tumors. Multiple molecular forms of BNP were found to be present in the tumor tissues of pheochromocytoma and aldosteronoma.