Frequent air travel and long flight duration makes the study of airliner cabin environmental quality a topic of utmost importance. Ventilation effectiveness is one of the more crucial factors affecting air quality in any environment. Ventilation effectiveness, along with the overall ventilation rate, is a measure of the ability of the air distribution system to remove internally generated pollutants or contaminants from a given space. Because of the high occupant density in an aircraft cabin, local variations in ventilation are important as a passenger will occupy the same space for the duration of the flight. Poor ventilation in even a small portion of the cabin could impact multiple people for extended time periods. In this study, the local effective ventilation rates and local ventilation effectiveness in an eleven row, full-scale, Boeing 767 cabin mockup were measured. These measurements were completed at each of the 77 seats in the mockup. Each seat was occupied by a heated mannequin. In order to simulate the thermal load inside the cabin, the mannequins were wrapped with a heating wire to generate approximately 100 W (341 BTU/hour) of heat. Carbon dioxide was used as a tracer gas for the experiments and the tracer gas decay method was employed to calculate the local effective ventilation rate and local ventilation effectiveness. The overall ventilation rate, based on total supply air flow, was approximately 27 air changes per hour. Local ventilation effectiveness ranged from 0.86 to 1.02 with a mean value of 0.94. These ventilation effectiveness values are higher than typically found in other indoor applications and are likely due to the relatively high airspeeds present in the aircraft cabin and the high degree of mixing they provide. The uniformity is also good with no areas of particularly low ventilation effectiveness being identified. No clear patterns with respect to seat location, window versus center versus aisle, were found.