1. Rabbits, previously sensitized to egg albumen, were anaesthetized and then rendered anaphylactic by a further injection of egg albumen; total lung conductance of flow, lung compliance, breathing rate, tidal volume, end-tidal CO2%, systemic arterial and right atrial blood pressures and heart rate were measured. Before induction of anaphylaxis, some rabbits were vagotomized, some had their vagi cooled to block differential conduction, and others were paralysed and artificially ventilated to minimize secondary changes in afferent activity from the lungs and in blood gas tensions.