Several artificial rainwater samples and a natural sample of road dust have been analysed for trimethyl-lead under the aegis of a European Union Measurement and Testing (Bureau of Community Reference - BCR) intercomparison exercise, using a new and simplified purge and trap ethylation technique. Levels of trimethyllead found have been similar to those reported at lower levels from the natural environment. The method has been successful in the presence of excess amounts of inorganic lead, even for organic lead levels one tenth of those recently reported for the natural environment.