The hybrid* passenger road vehicle presents a difficult problem when one considers establishing meaningful test procedures for determining performance and energy and fuel consumption characteristics. This is due to the continuum of possibilities of division of use of the energy stores available for propulsion during the drive mission. The continuum, or spectrum, varies from one extreme operation as an all-electric, where no on-board liquid petroleum fuel is used, to the other extreme operation as an all-ICE, where no electricity is used.This paper reviews the background of hybrids and discusses testing to date of some hybrids. Three proposed methods of testing hybrids that have been published or proposed, are examined. The results presented are mainly those determined by IEC TC/69 WG5 “Hybrid Electric Road Vehicles” at a meeting in London on September 17 and 18, 1981. Several components of a test procedure have been approved, but no recommended complete test procedure, even for a specific mission, has as yet received anything but tentative approval.