Nerve growth factor-induced clone B (NGFI-B; NR4A1) and Nur-related factor 1 (Nurr1; NR4A2) are members of NGFI-B family of orphan receptors. We recently demonstrated induction of CYP11B2 (aldosterone synthase) by Nurr1 and NGFI-B, suggesting possible important roles of these transcriptional factors in the regulation of adrenocortical steroidogenesis. Therefore, we immunolocalized Nurr1 and NGFI-B in various human adrenal specimens to study their biological significance. In nonpathological adrenal glands (n = 25), Nurr1 and NGFI-B immunoreactivities were detected at high levels in the fetal definitive zone or postnatal zona glomerulosa. NGFI-B immunoreactivity was increased according to development in the zona fasciculata, reaching a level similar to that in the zona glomerulosa in adult adrenal cortex. In adrenocortical neoplasms (n = 44), Nurr1 immunoreactivity was higher in aldosteronoma than in Cushing's adenoma or adrenocortical carcinoma. NGFI-B immunoreactivity was also higher in aldosteronoma than in adrenocortical carcinoma, but was not significantly different among the types of adenoma. Both Nurr1 and NGFI-B mRNA expressions were correlated with their immunoreactivities in adrenocortical neoplasms (n = 23), and mRNA expression of Nurr1 was significantly (P < 0.0001) associated with that of CYP11B2. These results suggest that the expression of Nurr1 and NGFI-B plays an important role in human adrenal cortex and its neoplasms, including possible regulation of steroidogenesis.