Changes of phosphates related to energetic metabolism such as PCr, Pi, ATP in C57 mouse brainin hypoxia were observed noninvasively by 31P in vivo NMR method. When the content of oxygen wasreduced to 5%, the concentrations of PCr, ATP decreased while Pi increased, pH of brain cell decreasedto 6.83 ~ 6.93. Mice were reoxygenated when the ratio of peak heights of Pi to PCr were about 1.Those that the ratio of pi after and before reoxygenation were larger than 1 and pH in reoxygenationincreased immediately, co...