1. Plasma cadmium and zinc were determined by atomic absorption spectrophotometry in inferior venal caval or peripheral venous blood in thirty hypertensive patients and fifteen normal subjects.
2. The mean plasma cadmium in hypertensive patients was significantly higher than in normal control subjects.
3. The plasma cadmium/zinc ratio was significantly greater in hypertensive patients.
4. There was a significant positive correlation between the plasma cadmium/zinc ratio and the mean arterial blood pressure.