['The adrenal cortex produces aldosterone, cortisol and androgens in response to ACTH and angiotensin II. To define the differential response of morphologically distinct cells of the adrenal cortex, we examined the phenotypical and functional characteristics of human adrenocortical cells.', 'Tumour growth factor-beta receptor-1 (TGFbeta-R1) and CYP-11 were found to be expressed predominantly in the zona fasciculata, whereas human leukocyte antigen (HLA-DR) and CYP-17 were localised to the zona reticularis. The angiotensin II receptor, AT-1, was found to be predominantly expressed in the zona glomerulosa. Adrenocortical cells, separated by density, yielded two distinct fractions which displayed differential growth patterns. Lipid-rich cells of fraction I expressed TGFbeta-R1 and produced significantly more cortisol relative to androstenedione than unseparated or fraction II cells, whereas lipid-poor cells of fraction II expressed HLA-DR and produced more androstenedione relative to cortisol in the presence of ACTH. Aldosterone production by fraction II was significantly greater than fraction I or unseparated cells. TGFbeta-R1-positive fasciculata-type cells separated into fraction I and HLA-DR-positive cells consistent with reticularis cells separated into fraction II. Aldosterone-producing cells indicative of glomerulosa cells separated into fraction II.'] Is differential production of adrenal steroids by purified cells of the human adrenal cortex relative rather than absolute?