Extensive tests have been carried out with European and Japanese cars to investigate the occurrence of vapour lock and related problems under hot-weather conditions. Different criteria, based on gasoline inspection properties, were evaluated for their ability to control hot-fuel handling performance. Considerable market experience has been accumulated with the flexible control, RVP (mbar) + 7E70, which is preferred by the authors to the vapour/liquid ratio type of control because it is far easier to use in routine refinery applications and control. However, the two types of control are equivalent in their ability to predict the performance of a wide range of gasolines, including those which may result from reductions in lead content. In their tolerance to gasoline volatility, the European and Japanese cars are very similar to the catalyst-equipped California models tested by the CRC in 1975.