The effects of beta-blocker therapy with either nadolol or propranolol were compared during therapy with hydrochlorothiazide (HCTZ) 50 mg b.i.d. on glomerular filtration rate (GFR), effective renal plasma flow (ERPF), effective renal blood flow (ERBF), blood pressure, and heart rate in 22 patients with essential hypertension and mild to moderate renal insufficiency. The clearances of inulin and para-aminohippurate (PAH) were used to estimate renal hemodynamic measurements. These parameters were determined after 2 weeks of HCTZ plus placebo and at 1, 3, and 6 months after the addition of beta-blocker to HCTZ. Significant reductions in blood pressure and heart rate were seen, but no significant reduction of renal hemodynamics were seen with either beta-blocker-HCTZ combination. Since 50% of the patients in each drug group were either Black or White, hemodynamic data were also analyzed by race. One month after beta-blocker addition there was a slight reduction of GFR in both Whites (47 +/- 6 vs. 40 +/- 5 ml/min, p greater than .05) and Blacks (44 +/- 5 vs. 40 +/- 6 ml/min, p less than .05). By month 6, GFR in Whites rose to 57 +/- 9 ml/min, whereas in Blacks it fell significantly to 36 +/- 6 ml/min (p less than .01). Similarly, at month 1, ERBF declined by 12% and 13% in Whites and Blacks, respectively. However, at month 6, ERBF rose by 28% in Whites and remained 11% lower in Blacks, p less than .05. In summary, in the group as a whole neither beta-blocker significantly altered renal hemodynamics when added to HCTZ therapy.(ABSTRACT TRUNCATED AT 250 WORDS)