The effects of two beta-adrenoceptor blockers, the beta1-selective metoprolol and the non-selective propranolol, was studied in high renin patients (n = 15) with very high pretreatment blood pressures. Ten of the patients had essential hypertension and five renal artery stenosis. From high blood pressure values after six weeks on placebo, there was a pronounced drop in both supine and standing blood pressures in both groups with a small to moderate dose of beta-blocker, thus showing that the good blood pressure control in high renin patients is not connected to blockade of beta2-receptors or to the aetiology of the hypertension. In patients with essential hypertension who were treated with metoprolol, a significant positive correlation (r = 0.66, n = 10) was also found between the fall in blood pressure and the fall in plasma renin activity. Values for glomerular filtration rate (GFR) before and after treatment were unchanged throughout the whole spectrum of GFR from those values indicating substantially decreased kidney function up to normal values.