Enhanced sensitivity of blood pressure to salt intake is observed in many hypertensive patients. The kidney plays a key role in the development of hypertension including salt-sensitive hypertension. In this study, we used BOLD MRI to examine the temporal response of renal medullary and cortical oxygenation levels during saline infusion in a small set of young subjects. The results showed that during the period of fast saline infusion, tissue oxygenation levels remained almost constant in the cortex but showed 10%-15% average reduction in the medulla. The responses, however, varied between subjects, which may reflect differences in salt-sensitive versus salt-insensitive individuals.