As a result of the Council Decision 85/338/EEC, the Commission of the European Communities (DG XI) realised in the period 1987 to 1990 plans to gather EC wide information on emissions of pollutants into the air in a consistent form. This information is broken down into several source categories of which road traffic is an important part. In order to improve on the accuracy of the emission data, working groups were set up to help in emissions forecasting. The CORINAIR Working Group on Emmission factors for Calculating Emissions from Road Traffic developed a methodology including appropriate emission factors for the reference year 1985 (Eggleston et al 1989). A computer program was also developed (Samaras et al 1989). In 1991 the group has been re- convened with the aim of making proposals to EC member states on a set of emission factors for the 1990 inventory. This report describes the methodology developed by the working group. The emission factors proposed cover: hot emissions; cold starts; evaporative emissions. Data in tabular form is given on emissions by engine capacity, type of fuel used, and speed of vehicle.