Nitrous oxide (N2O) concentrations in the ambient atmosphere were measured by gas chromatography during surgical anesthesia. Levels in the recovery room were affected not only by the N2O content in the expiratory air of postanesthetic patients and personnel but also by N2O levels in the operating rooms. With the onset of N2O anesthesia in operating rooms, gases blow into all adjacent areas; while this level is relatively low, operating-suite personnel cannot escape some exposure to N2O.