In order to explore the role of brain atrial natriuretic peptide (ANP) in regulating water and electrolytes, the changes of the ANP content of various brain areas in the status of high salt intake and in 3/4 nephrectomy rats. In control group, a wide distribution of ANP was observed in different areas of the brain. The amount of daily water intake and urine were larger, and urine sodium concentration was lower in the 3/4 nephrectomy group than those in the control group (P < 0.05). In the ten nuclei we have studied, ANP content was not significantly different from that of the control (P > 0.05). In the high salt group, water intake, urine volume and urine sodium concentration were significantly higher than those in the control. In this group, brain ANP increased in the periventricular nuclues (PVN) and arcute nucleus (Arc) (P < 0.05). The results indicate that ANP in anteroventral region of the third ventricle (AV3V) might play important role in the regulation of water and electolytes.