Intracellular pH (pHi) and lactate were monitored in a superfused brain slice preparation using NMR spectroscopy in order to study the role of lactate washout in maintenance of pHi during hypoxia. Data are consistence with a functioning lactate-H+ cotransport in the energetically intact cerebral cortex. This pathway is not, however, linked to regulation of pHi during energy failure with external pH of 6.8 and thus appears not to have physiological impact in H+ homeostasis during cerebral hypoxia.