1. Plasma zinc (μg/100 ml) was determined by atomic absorption spectrophotometry in ninety renal venous, inferior vena caval or peripheral venous specimens obtained from fifteen normal control subjects and thirty hypertensive patients, none of whom had renal failure.
2. Peripheral or central venous plasma zinc levels in ten patients with essential hypertension were not significantly different from those of control subjects. There were, however, significantly lower venous plasma zinc levels found in sixteen patients with renal artery stenosis and four patients with renal parenchymal disease.
3. The only clinical variable found to have a significant inverse correlation with plasma zinc was the mean arterial blood pressure.
4. There were no significant differences in zinc concentrations between central venous and renal venous plasma specimens.