1. The presence of high-affinity sites for [3H]-aldosterone was shown in the normal human renal tissue.
2. [3H]Aldosterone and [3H]dexamethasone binding were studied in human renal adenocarcinoma and in uninvolved external cortex, in 22 patients undergoing nephrectomy for renal adenocarcinoma. Tissue incubations were performed with either [3H]aldosterone (5 × 10−10 mol/l; 5 × 10−9 mol/l in the presence of unlabelled glucocorticoids) or [3H]dexamethasone (5 × 10−9 mol/l).
3. Cytosol [3H]aldosterone binding was six- to seven-fold lower (P < 0·001) in neoplastic than normal tissue. [3H]Dexamethasone binding was about twofold higher in neoplastic than in normal tissue. This difference was not significant.
4. Nuclear uptake experiments showed that, both in cytosol fractions and nuclei, [3H]aldosterone binding was lower in adenocarcinoma than in normal cortex.
5. The very low binding of [3H] aldosterone suggests that mineralocorticoid receptors are absent in renal adenocarcinoma, an hypothesis in line with the proximal origin of these tumours.