This note describes measurements of the mass-specific extinction coefficient, sigma(s), of carbonaceous aerosol produced during hydrocarbon combustion. Measurements of sigma(s) were obtained by laser extinction lambda = 632 nm. The aerosol was generated using a laminar diffusion flame, and the mass-specific extinction coefficient determined as a function of the global equivalence ratio, phi. The elemental carbon content of the aerosol was also determined with respect to phi. A relationship was developed between the elemental carbon/total carbon (EC/TC) ratio and sigma(s). A simple method of producing laboratory aerosol with controlled EC/TC ratio is also presented. Crown Copyright (C) 2004 Published by Elsevier Ltd. All rights reserved.