Methods of measuring electrical bonding of large, complex structures such as aircraft are discussed. The importance of measurement method design and result interpretation are stressed. The methods which are described are either large scale, such as potential plotting, potential mapping and infra-red scanning, or examine a small area, such as the resistance of individual fasteners. These methods have all been usedin situon service aircraft or large mock-ups. The limitations on the measurement methods are pointed out and the potential uses of the results, to predict poor bonding areas, set specifications etc., suggested.