The study consisted of two parts: 1. The standard system in use at our hospital for gas delivery under the drapes during eye surgery under local anaesthesia was compared with one incorporating a venturi. 2. The oxygen concentration at the operation site was measured with three methods of draping using the two systems. Twenty-three patients and thirty-one volunteers from the operating room staff were subjected to operating conditions and gas concentrations and certain vital signs measured using both systems. The subjective response of the volunteers, none of whom had blocks or premedication, was noted. The burden of rebreathing seen with a significant proportion of cases using 6 l/min of fresh gas flow was not seen when the venturi system was used. The safety from fire hazard using 26% oxygen and diathermy was demonstrated with occlusive and free draping.