Abstract Nitrous oxide is a widely used anesthetic gas. The aim of this study was to investigate the effect of this agent on inflammatory side effects in the brain. The cerebral microcirculation of Mongolian gerbils was investigated by fluorescent intravital microscopy for up to 7 h after induction of anesthesia. Anesthesia was induced and maintained with isoflurane or halothane alone or in combination with nitrous oxide (70%). The number of leukocytes that were rolling along and firmly adherent to the endothelial wall of cerebral venules was significantly elevated in animals anesthetized with nitrous oxide in combination with isoflurane and halothane compared to isoflurane and halothane alone. A significantly increased number of neutrophil granulocytes invading the brain parenchyma in histological slices from animals treated with the combination of isoflurane or halothane and nitrous oxide compared to controls treated with isoflurane or halothane alone was observed. Our data show that prolonged anesthesia with nitrous oxide induces inflammation of the cerebral microcirculation and brain.