Propane and natural gas vehicles are perceived by the public as having low exhaust emissions. However, the results of an emissions inspection program started in British Columbia in 1992 indicate that this is not usually the case. The study reported in this paper addresses two questions which arose from these results: ‘Why do propane and natural gas vehicles fail the inspection in such large numbers?’ and ‘What needs to be done to fix the problem?’The project comprises three phases.Phase one is to establish the profile of the alternative fuel vehicle fleet in the Province; the way in which they usually fail emissions inspection; the types of repairs received after failing; and the effectiveness of those repairs in reducing emissions.Phase two is to formulate general repair stategies which can be applied in the great majority of cases and therefore effectively become recognized by government agencies, the conversion industry, and the repair industry. The desire is to achieve the maximum emissions reduction benefit as effectively as possible, for as many vehicles as possible, all within acceptable costs.Phase three will be full implementation of vehicle upgrade requirements throughout the Province. This is scheduled to start January 1996 in the Lower Fraser Valley, and expand to the whole province in July 1996.This paper is essentially concerned with phase one of the project.